如何首先使用遷移向 Entity Framework 4.3 代碼中的列添加描述？

Question

我首先使用 Entity Framework 4.3.1 代碼進行顯式遷移。 如何在實體配置類或遷移中添加列的描述，使其最終成為 SQL 服務器（例如 2008 R2）中列的描述？

我知道我可以為DbMigration class 編寫一個擴展方法，它將sp_updateextendedproperty或sp_addextendedproperty過程調用注冊為遷移事務中的 sql 遷移操作，並在遷移Up方法中創建表后調用該擴展。 但是有沒有一種我還沒有發現的優雅的內置方式？ 最好有一個屬性，遷移的更改檢測邏輯可以在腳手架遷移中獲取並生成適當的方法調用。

Answer 1

我也需要這個。 所以我花了一天，這里是：

代碼

    public class DbDescriptionUpdater<TContext>
        where TContext : System.Data.Entity.DbContext
    {
        public DbDescriptionUpdater(TContext context)
        {
            this.context = context;
        }

        Type contextType;
        TContext context;
        DbTransaction transaction;
        public void UpdateDatabaseDescriptions()
        {
            contextType = typeof(TContext);
            this.context = context;
            var props = contextType.GetProperties(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public);
            transaction = null;
            try
            {
                context.Database.Connection.Open();
                transaction = context.Database.Connection.BeginTransaction();
                foreach (var prop in props)
                {
                    if (prop.PropertyType.InheritsOrImplements((typeof(DbSet<>))))
                    {
                        var tableType = prop.PropertyType.GetGenericArguments()[0];
                        SetTableDescriptions(tableType);
                    }
                }
                transaction.Commit();
            }
            catch
            {
                if (transaction != null)
                    transaction.Rollback();
                throw;
            }
            finally
            {
                if (context.Database.Connection.State == System.Data.ConnectionState.Open)
                    context.Database.Connection.Close();
            }
        }

        private void SetTableDescriptions(Type tableType)
        {
            string fullTableName = context.GetTableName(tableType);
            Regex regex = new Regex(@"(\[\w+\]\.)?\[(?<table>.*)\]");
            Match match = regex.Match(fullTableName);
            string tableName;
            if (match.Success)
                tableName = match.Groups["table"].Value;
            else
                tableName = fullTableName;

            var tableAttrs = tableType.GetCustomAttributes(typeof(TableAttribute), false);
            if (tableAttrs.Length > 0)
                tableName = ((TableAttribute)tableAttrs[0]).Name;
            foreach (var prop in tableType.GetProperties(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance))
            {
                if (prop.PropertyType.IsClass && prop.PropertyType != typeof(string))
                    continue;
                var attrs = prop.GetCustomAttributes(typeof(DisplayAttribute), false);
                if (attrs.Length > 0)
                    SetColumnDescription(tableName, prop.Name, ((DisplayAttribute)attrs[0]).Name);
            }
        }

        private void SetColumnDescription(string tableName, string columnName, string description)
        {
            string strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "','column',null) where objname = N'" + columnName + "';";
            var prevDesc = RunSqlScalar(strGetDesc);
            if (prevDesc == null)
            {
                RunSql(@"EXEC sp_addextendedproperty 
@name = N'MS_Description', @value = @desc,
@level0type = N'Schema', @level0name = 'dbo',
@level1type = N'Table',  @level1name = @table,
@level2type = N'Column', @level2name = @column;",
                                                       new SqlParameter("@table", tableName),
                                                       new SqlParameter("@column", columnName),
                                                       new SqlParameter("@desc", description));
            }
            else
            {
                RunSql(@"EXEC sp_updateextendedproperty 
@name = N'MS_Description', @value = @desc,
@level0type = N'Schema', @level0name = 'dbo',
@level1type = N'Table',  @level1name = @table,
@level2type = N'Column', @level2name = @column;",
                                                       new SqlParameter("@table", tableName),
                                                       new SqlParameter("@column", columnName),
                                                       new SqlParameter("@desc", description));
            }
        }

        DbCommand CreateCommand(string cmdText, params SqlParameter[] parameters)
        {
            var cmd = context.Database.Connection.CreateCommand();
            cmd.CommandText = cmdText;
            cmd.Transaction = transaction;
            foreach (var p in parameters)
                cmd.Parameters.Add(p);
            return cmd;
        }
        void RunSql(string cmdText, params SqlParameter[] parameters)
        {
            var cmd = CreateCommand(cmdText, parameters);
            cmd.ExecuteNonQuery();
        }
        object RunSqlScalar(string cmdText, params SqlParameter[] parameters)
        {
            var cmd = CreateCommand(cmdText, parameters);
            return cmd.ExecuteScalar();
        }

    }
    public static class ReflectionUtil
    {

        public static bool InheritsOrImplements(this Type child, Type parent)
        {
            parent = ResolveGenericTypeDefinition(parent);

            var currentChild = child.IsGenericType
                                   ? child.GetGenericTypeDefinition()
                                   : child;

            while (currentChild != typeof(object))
            {
                if (parent == currentChild || HasAnyInterfaces(parent, currentChild))
                    return true;

                currentChild = currentChild.BaseType != null
                               && currentChild.BaseType.IsGenericType
                                   ? currentChild.BaseType.GetGenericTypeDefinition()
                                   : currentChild.BaseType;

                if (currentChild == null)
                    return false;
            }
            return false;
        }

        private static bool HasAnyInterfaces(Type parent, Type child)
        {
            return child.GetInterfaces()
                .Any(childInterface =>
                {
                    var currentInterface = childInterface.IsGenericType
                        ? childInterface.GetGenericTypeDefinition()
                        : childInterface;

                    return currentInterface == parent;
                });
        }

        private static Type ResolveGenericTypeDefinition(Type parent)
        {
            var shouldUseGenericType = true;
            if (parent.IsGenericType && parent.GetGenericTypeDefinition() != parent)
                shouldUseGenericType = false;

            if (parent.IsGenericType && shouldUseGenericType)
                parent = parent.GetGenericTypeDefinition();
            return parent;
        }
    }

    public static class ContextExtensions
    {
        public static string GetTableName(this DbContext context, Type tableType)
        {
            MethodInfo method = typeof(ContextExtensions).GetMethod("GetTableName", new Type[] { typeof(DbContext) })
                             .MakeGenericMethod(new Type[] { tableType });
            return (string)method.Invoke(context, new object[] { context });
        }
        public static string GetTableName<T>(this DbContext context) where T : class
        {
            ObjectContext objectContext = ((IObjectContextAdapter)context).ObjectContext;

            return objectContext.GetTableName<T>();
        }

        public static string GetTableName<T>(this ObjectContext context) where T : class
        {
            string sql = context.CreateObjectSet<T>().ToTraceString();
            Regex regex = new Regex("FROM (?<table>.*) AS");
            Match match = regex.Match(sql);

            string table = match.Groups["table"].Value;
            return table;
        }
    }

如何使用

在您的Migrations/Configuration.cs文件中，將其添加到Seed方法的末尾：

DbDescriptionUpdater<ContextClass> updater = new DbDescriptionUpdater<ContextClass>(context);
updater.UpdateDatabaseDescriptions();

然后在 Package Manager Console 中鍵入update-database並按 Enter。 而已。

該代碼使用實體 class 屬性上的[Display(Name="Description here")]屬性來設置描述。

請報告任何錯誤或提出改進建議。

謝謝

我已經使用了其他人的這些代碼，我想說聲謝謝：

添加列說明

檢查 class 是否派生自通用 class

從實體框架元數據中獲取數據庫表名

C#中的Generics，使用變量的類型作為參數

Answer 2

注意對當前的答案相當滿意（但工作的道具，）。 我想要一種方法來提取我的類中現有的注釋標記，而不是使用屬性，而且在我看來，我不知道為什么微軟不支持這個，因為它看起來很明顯應該存在！

首先，開啟XML文檔文件：Project Properties->Build->XML documentation file->App_Data\YourProjectName.XML

其次，將文件作為嵌入式資源包含在內。 構建您的項目，go 到 App_Data，顯示隱藏文件並包含生成的 XML 文件。 Select 嵌入資源，如果更新則復制（這是可選的，您可以明確指定路徑，但我認為這更清晰）。 請注意，您必須使用此方法，因為標記不存在於程序集中，並且可以避免您定位 XML 的存儲位置。

這是代碼實現，它是已接受答案的修改版本：

public class SchemaDescriptionUpdater<TContext> where TContext : DbContext
{
    Type contextType;
    TContext context;
    DbTransaction transaction;
    XmlAnnotationReader reader;
    public SchemaDescriptionUpdater(TContext context)
    {
        this.context = context;
        reader = new XmlAnnotationReader();
    }
    public SchemaDescriptionUpdater(TContext context, string xmlDocumentationPath)
    {
        this.context = context;
        reader = new XmlAnnotationReader(xmlDocumentationPath);
    }

    public void UpdateDatabaseDescriptions()
    {
        contextType = typeof(TContext);
        var props = contextType.GetProperties(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public);
        transaction = null;
        try
        {
            context.Database.Connection.Open();
            transaction = context.Database.Connection.BeginTransaction();
            foreach (var prop in props)
            {
                if (prop.PropertyType.InheritsOrImplements((typeof(DbSet<>))))
                {
                    var tableType = prop.PropertyType.GetGenericArguments()[0];
                    SetTableDescriptions(tableType);
                }
            }
            transaction.Commit();
        }
        catch
        {
            if (transaction != null)
                transaction.Rollback();
            throw;
        }
        finally
        {
            if (context.Database.Connection.State == System.Data.ConnectionState.Open)
                context.Database.Connection.Close();
        }
    }

    private void SetTableDescriptions(Type tableType)
    {
        string fullTableName = context.GetTableName(tableType);
        Regex regex = new Regex(@"(\[\w+\]\.)?\[(?<table>.*)\]");
        Match match = regex.Match(fullTableName);
        string tableName;
        if (match.Success)
            tableName = match.Groups["table"].Value;
        else
            tableName = fullTableName;

        var tableAttrs = tableType.GetCustomAttributes(typeof(TableAttribute), false);
        if (tableAttrs.Length > 0)
            tableName = ((TableAttribute)tableAttrs[0]).Name;

        // set the description for the table
        string tableComment = reader.GetCommentsForResource(tableType, null, XmlResourceType.Type);
        if (!string.IsNullOrEmpty(tableComment))
            SetDescriptionForObject(tableName, null, tableComment);

        // get all of the documentation for each property/column
        ObjectDocumentation[] columnComments = reader.GetCommentsForResource(tableType);
        foreach (var column in columnComments)
        {
            SetDescriptionForObject(tableName, column.PropertyName, column.Documentation);
        }
    }

    private void SetDescriptionForObject(string tableName, string columnName, string description)
    {
        string strGetDesc = "";
        // determine if there is already an extended description
        if(string.IsNullOrEmpty(columnName))
            strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "',null,null);";
        else
            strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "','column',null) where objname = N'" + columnName + "';";
        var prevDesc = (string)RunSqlScalar(strGetDesc);

        var parameters = new List<SqlParameter>
        {
            new SqlParameter("@table", tableName),
            new SqlParameter("@desc", description)
        };

        // is it an update, or new?
        string funcName = "sp_addextendedproperty";
        if (!string.IsNullOrEmpty(prevDesc))
            funcName = "sp_updateextendedproperty";

        string query = @"EXEC " + funcName + @" @name = N'MS_Description', @value = @desc,@level0type = N'Schema', @level0name = 'dbo',@level1type = N'Table',  @level1name = @table";

        // if a column is specified, add a column description
        if (!string.IsNullOrEmpty(columnName))
        {
            parameters.Add(new SqlParameter("@column", columnName));
            query += ", @level2type = N'Column', @level2name = @column";
        }
        RunSql(query, parameters.ToArray());
    }

    DbCommand CreateCommand(string cmdText, params SqlParameter[] parameters)
    {
        var cmd = context.Database.Connection.CreateCommand();
        cmd.CommandText = cmdText;
        cmd.Transaction = transaction;
        foreach (var p in parameters)
            cmd.Parameters.Add(p);
        return cmd;
    }
    void RunSql(string cmdText, params SqlParameter[] parameters)
    {
        var cmd = CreateCommand(cmdText, parameters);
        cmd.ExecuteNonQuery();
    }
    object RunSqlScalar(string cmdText, params SqlParameter[] parameters)
    {
        var cmd = CreateCommand(cmdText, parameters);
        return cmd.ExecuteScalar();
    }

}

public static class ReflectionUtil
{
    public static bool InheritsOrImplements(this Type child, Type parent)
    {
        parent = ResolveGenericTypeDefinition(parent);

        var currentChild = child.IsGenericType
                               ? child.GetGenericTypeDefinition()
                               : child;

        while (currentChild != typeof(object))
        {
            if (parent == currentChild || HasAnyInterfaces(parent, currentChild))
                return true;

            currentChild = currentChild.BaseType != null
                           && currentChild.BaseType.IsGenericType
                               ? currentChild.BaseType.GetGenericTypeDefinition()
                               : currentChild.BaseType;

            if (currentChild == null)
                return false;
        }
        return false;
    }

    private static bool HasAnyInterfaces(Type parent, Type child)
    {
        return child.GetInterfaces()
            .Any(childInterface =>
            {
                var currentInterface = childInterface.IsGenericType
                    ? childInterface.GetGenericTypeDefinition()
                    : childInterface;

                return currentInterface == parent;
            });
    }

    private static Type ResolveGenericTypeDefinition(Type parent)
    {
        var shouldUseGenericType = true;
        if (parent.IsGenericType && parent.GetGenericTypeDefinition() != parent)
            shouldUseGenericType = false;

        if (parent.IsGenericType && shouldUseGenericType)
            parent = parent.GetGenericTypeDefinition();
        return parent;
    }
}

public static class ContextExtensions
{
    public static string GetTableName(this DbContext context, Type tableType)
    {
        MethodInfo method = typeof(ContextExtensions).GetMethod("GetTableName", new Type[] { typeof(DbContext) })
                         .MakeGenericMethod(new Type[] { tableType });
        return (string)method.Invoke(context, new object[] { context });
    }
    public static string GetTableName<T>(this DbContext context) where T : class
    {
        ObjectContext objectContext = ((IObjectContextAdapter)context).ObjectContext;

        return objectContext.GetTableName<T>();
    }

    public static string GetTableName<T>(this ObjectContext context) where T : class
    {
        string sql = context.CreateObjectSet<T>().ToTraceString();
        Regex regex = new Regex("FROM (?<table>.*) AS");
        Match match = regex.Match(sql);

        string table = match.Groups["table"].Value;
        return table;
    }
}

而從 visual studio 中獲取注釋標記的 class 生成了 XML 文檔文件：

public class XmlAnnotationReader
{
    public string XmlPath { get; protected internal set; }
    public XmlDocument Document { get; protected internal set; }

    public XmlAnnotationReader()
    {
        var assembly = Assembly.GetExecutingAssembly();
        string resourceName = String.Format("{0}.App_Data.{0}.XML", assembly.GetName().Name);
        this.XmlPath = resourceName;
        using (Stream stream = assembly.GetManifestResourceStream(resourceName))
        {
            using (StreamReader reader = new StreamReader(stream))
            {
                XmlDocument doc = new XmlDocument();
                //string result = reader.ReadToEnd();
                doc.Load(reader);
                this.Document = doc;
            }
        }
    }

    public XmlAnnotationReader(string xmlPath)
    {
        this.XmlPath = xmlPath;
        if (File.Exists(xmlPath))
        {
            XmlDocument doc = new XmlDocument();
            doc.Load(this.XmlPath);
            this.Document = doc;
        }
        else
            throw new FileNotFoundException(String.Format("Could not find the XmlDocument at the specified path: {0}\r\nCurrent Path: {1}", xmlPath, Assembly.GetExecutingAssembly().Location));
    }

    /// <summary>
    /// Retrievethe XML comments documentation for a given resource
    /// Eg. ITN.Data.Models.Entity.TestObject.MethodName
    /// </summary>
    /// <returns></returns>
    public string GetCommentsForResource(string resourcePath, XmlResourceType type)
    {

        XmlNode node = Document.SelectSingleNode(String.Format("//member[starts-with(@name, '{0}:{1}')]/summary", GetObjectTypeChar(type), resourcePath));
        if (node != null)
        {
            string xmlResult = node.InnerText;
            string trimmedResult = Regex.Replace(xmlResult, @"\s+", " ");
            return trimmedResult;
        }
        return string.Empty;
    }

    /// <summary>
    /// Retrievethe XML comments documentation for a given resource
    /// Eg. ITN.Data.Models.Entity.TestObject.MethodName
    /// </summary>
    /// <returns></returns>
    public ObjectDocumentation[] GetCommentsForResource(Type objectType)
    {
        List<ObjectDocumentation> comments = new List<ObjectDocumentation>();
        string resourcePath = objectType.FullName;

        PropertyInfo[] properties = objectType.GetProperties();
        FieldInfo[] fields = objectType.GetFields();
        List<ObjectDocumentation> objectNames = new List<ObjectDocumentation>();
        objectNames.AddRange(properties.Select(x => new ObjectDocumentation() { PropertyName = x.Name, Type = XmlResourceType.Property }).ToList());
        objectNames.AddRange(properties.Select(x => new ObjectDocumentation() { PropertyName = x.Name, Type = XmlResourceType.Field }).ToList());

        foreach (var property in objectNames)
        {
            XmlNode node = Document.SelectSingleNode(String.Format("//member[starts-with(@name, '{0}:{1}.{2}')]/summary", GetObjectTypeChar(property.Type), resourcePath, property.PropertyName ));
            if (node != null)
            {
                string xmlResult = node.InnerText;
                string trimmedResult = Regex.Replace(xmlResult, @"\s+", " ");
                property.Documentation = trimmedResult;
                comments.Add(property);
            }
        }
        return comments.ToArray();
    }

    /// <summary>
    /// Retrievethe XML comments documentation for a given resource
    /// </summary>
    /// <param name="objectType">The type of class to retrieve documenation on</param>
    /// <param name="propertyName">The name of the property in the specified class</param>
    /// <param name="resourceType"></param>
    /// <returns></returns>
    public string GetCommentsForResource(Type objectType, string propertyName, XmlResourceType resourceType)
    {
        List<ObjectDocumentation> comments = new List<ObjectDocumentation>();
        string resourcePath = objectType.FullName;

        string scopedElement = resourcePath;
        if (propertyName != null && resourceType != XmlResourceType.Type)
            scopedElement += "." + propertyName;
        XmlNode node = Document.SelectSingleNode(String.Format("//member[starts-with(@name, '{0}:{1}')]/summary", GetObjectTypeChar(resourceType), scopedElement));
        if (node != null)
        {
            string xmlResult = node.InnerText;
            string trimmedResult = Regex.Replace(xmlResult, @"\s+", " ");
            return trimmedResult;
        }
        return string.Empty;
    }

    private string GetObjectTypeChar(XmlResourceType type)
    {
        switch (type)
        {
            case XmlResourceType.Field:
                return "F";
            case XmlResourceType.Method:
                return "M";
            case XmlResourceType.Property:
                return "P";
            case XmlResourceType.Type:
                return "T";

        }
        return string.Empty;
    }
}

public class ObjectDocumentation
{
    public string PropertyName { get; set; }
    public string Documentation { get; set; }
    public XmlResourceType Type { get; set; }
}

public enum XmlResourceType
{
    Method,
    Property,
    Field,
    Type
}

Answer 3

你不能使用ExceuteSqlCommand方法嗎？ 在這里，您可以明確定義要添加到表中的任何元屬性。

http://msdn.microsoft.com/en-us/library/system.data.entity.database.executesqlcommand(v=vs.103).aspx

Answer 4

感謝Mr.Mahmoodvcs提供的出色解決方案。 請允許我修改它，只需將“DisplayAttribute”替換為“DescriptionAttribute”而不是使用：

[Display(Name="Description here")]

你將使用：

[Description("Description here")]

所以它也包括表格。

    public class DbDescriptionUpdater<TContext>
   where TContext : System.Data.Entity.DbContext
{
    public DbDescriptionUpdater(TContext context)
    {
        this.context = context;
    }

    Type contextType;
    TContext context;
    DbTransaction transaction;
    public void UpdateDatabaseDescriptions()
    {
        contextType = typeof(TContext);
        this.context = context;
        var props = contextType.GetProperties(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public);
        transaction = null;
        try
        {
            context.Database.Connection.Open();
            transaction = context.Database.Connection.BeginTransaction();
            foreach (var prop in props)
            {
                if (prop.PropertyType.InheritsOrImplements((typeof(DbSet<>))))
                {
                    var tableType = prop.PropertyType.GetGenericArguments()[0];
                    SetTableDescriptions(tableType);
                }
            }
            transaction.Commit();
        }
        catch
        {
            if (transaction != null)
                transaction.Rollback();
            throw;
        }
        finally
        {
            if (context.Database.Connection.State == System.Data.ConnectionState.Open)
                context.Database.Connection.Close();
        }
    }

    private void SetTableDescriptions(Type tableType)
    {
        string fullTableName = context.GetTableName(tableType);
        Regex regex = new Regex(@"(\[\w+\]\.)?\[(?<table>.*)\]");
        Match match = regex.Match(fullTableName);
        string tableName;
        if (match.Success)
            tableName = match.Groups["table"].Value;
        else
            tableName = fullTableName;

        var tableAttrs = tableType.GetCustomAttributes(typeof(TableAttribute), false);
        if (tableAttrs.Length > 0)
            tableName = ((TableAttribute)tableAttrs[0]).Name;
        var table_attrs = tableType.GetCustomAttributes(typeof(DescriptionAttribute), false);
        if (table_attrs != null && table_attrs.Length > 0)
            SetTableDescription(tableName, ((DescriptionAttribute)table_attrs[0]).Description);
        foreach (var prop in tableType.GetProperties(System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Instance))
        {
            if (prop.PropertyType.IsClass && prop.PropertyType != typeof(string))
                continue;
            var attrs = prop.GetCustomAttributes(typeof(DescriptionAttribute), false);
            if (attrs != null && attrs.Length > 0)
                SetColumnDescription(tableName, prop.Name, ((DescriptionAttribute)attrs[0]).Description);
        }
    }

    private void SetColumnDescription(string tableName, string columnName, string description)
    {

        string strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "','column',null) where objname = N'" + columnName + "';";
        var prevDesc = RunSqlScalar(strGetDesc);
        if (prevDesc == null)
        {
            RunSql(@"EXEC sp_addextendedproperty 
                @name = N'MS_Description', @value = @desc,
                @level0type = N'Schema', @level0name = 'dbo',
                @level1type = N'Table',  @level1name = @table,
                @level2type = N'Column', @level2name = @column;",
                                                   new SqlParameter("@table", tableName),
                                                   new SqlParameter("@column", columnName),
                                                   new SqlParameter("@desc", description));
        }
        else
        {
            RunSql(@"EXEC sp_updateextendedproperty 
                    @name = N'MS_Description', @value = @desc,
                    @level0type = N'Schema', @level0name = 'dbo',
                    @level1type = N'Table',  @level1name = @table,
                    @level2type = N'Column', @level2name = @column;",
                                                   new SqlParameter("@table", tableName),
                                                   new SqlParameter("@column", columnName),
                                                   new SqlParameter("@desc", description));
        }
    }
    private void SetTableDescription(string tableName,  string description)
    {

        string strGetDesc = "select [value] from fn_listextendedproperty('MS_Description','schema','dbo','table',N'" + tableName + "',null,null);";
        var prevDesc = RunSqlScalar(strGetDesc);
        if (prevDesc == null)
        {
            RunSql(@"EXEC sp_addextendedproperty 
                    @name = N'MS_Description', @value = @desc,
                    @level0type = N'Schema', @level0name = 'dbo',
                    @level1type = N'Table',  @level1name = @table;",
                                                   new SqlParameter("@table", tableName),
                                                   new SqlParameter("@desc", description));
        }
        else
        {
            RunSql(@"EXEC sp_updateextendedproperty 
                    @name = N'MS_Description', @value = @desc,
                    @level0type = N'Schema', @level0name = 'dbo',
                    @level1type = N'Table',  @level1name = @table;",
                                                   new SqlParameter("@table", tableName),
                                                   new SqlParameter("@desc", description));
        }
    }
    DbCommand CreateCommand(string cmdText, params SqlParameter[] parameters)
    {
        var cmd = context.Database.Connection.CreateCommand();
        cmd.CommandText = cmdText;
        cmd.Transaction = transaction;
        foreach (var p in parameters)
            cmd.Parameters.Add(p);
        return cmd;
    }
    void RunSql(string cmdText, params SqlParameter[] parameters)
    {
        var cmd = CreateCommand(cmdText, parameters);
        cmd.ExecuteNonQuery();
    }
    object RunSqlScalar(string cmdText, params SqlParameter[] parameters)
    {
        var cmd = CreateCommand(cmdText, parameters);
        return cmd.ExecuteScalar();
    }

}
public static class ReflectionUtil
{

    public static bool InheritsOrImplements(this Type child, Type parent)
    {
        parent = ResolveGenericTypeDefinition(parent);

        var currentChild = child.IsGenericType
                               ? child.GetGenericTypeDefinition()
                               : child;

        while (currentChild != typeof(object))
        {
            if (parent == currentChild || HasAnyInterfaces(parent, currentChild))
                return true;

            currentChild = currentChild.BaseType != null
                           && currentChild.BaseType.IsGenericType
                               ? currentChild.BaseType.GetGenericTypeDefinition()
                               : currentChild.BaseType;

            if (currentChild == null)
                return false;
        }
        return false;
    }

    private static bool HasAnyInterfaces(Type parent, Type child)
    {
        return child.GetInterfaces()
            .Any(childInterface =>
            {
                var currentInterface = childInterface.IsGenericType
                    ? childInterface.GetGenericTypeDefinition()
                    : childInterface;

                return currentInterface == parent;
            });
    }

    private static Type ResolveGenericTypeDefinition(Type parent)
    {
        var shouldUseGenericType = true;
        if (parent.IsGenericType && parent.GetGenericTypeDefinition() != parent)
            shouldUseGenericType = false;

        if (parent.IsGenericType && shouldUseGenericType)
            parent = parent.GetGenericTypeDefinition();
        return parent;
    }
}

public static class ContextExtensions
{
    public static string GetTableName(this DbContext context, Type tableType)
    {
        MethodInfo method = typeof(ContextExtensions).GetMethod("GetTableName", new Type[] { typeof(DbContext) })
                         .MakeGenericMethod(new Type[] { tableType });
        return (string)method.Invoke(context, new object[] { context });
    }
    public static string GetTableName<T>(this DbContext context) where T : class
    {
        ObjectContext objectContext = ((IObjectContextAdapter)context).ObjectContext;

        return objectContext.GetTableName<T>();
    }

    public static string GetTableName<T>(this ObjectContext context) where T : class
    {
        string sql = context.CreateObjectSet<T>().ToTraceString();
        Regex regex = new Regex("FROM (?<table>.*) AS");
        Match match = regex.Match(sql);

        string table = match.Groups["table"].Value;
        return table;
    }
}

Answer 5

雖然問題是關於 EF4 的，但這個答案針對的是 EF6，考慮到自提出問題以來經過的時間，這應該是合適的。

我認為 Comments 屬於 Migration Up和Down方法，而不是某種Seed方法。

因此，正如@MichaelBrown 所建議的那樣，首先啟用 XML 文檔 output 並將文檔文件作為嵌入式資源包含在您的項目中。

然后，讓我們使用Convention將注釋轉換為表/列注釋。 對於多行注釋和去除過多的空格等問題，需要進行一些調整。

public class CommentConvention : Convention
{
    public const string NewLinePlaceholder = "<<NEWLINE>>";

    public CommentConvention()
    {
        var docuXml = new XmlDocument();

        // Read the documentation xml
        using (var commentStream = Assembly.GetExecutingAssembly().GetManifestResourceStream("Namespace.Documentation.xml"))
        {
            docuXml.Load(commentStream);
        }

        // configure class/table comment
        Types()
            .Having(pi => docuXml.SelectSingleNode($"//member[starts-with(@name, 'T:{pi?.FullName}')]/summary"))
            .Configure((c, a) =>
            {
                c.HasTableAnnotation("Comment", GetCommentTextWithNewlineReplacement(a));
            });

        // configure property/column comments
        Properties()
            .Having(pi =>
                docuXml.SelectSingleNode(
                    $"//member[starts-with(@name, 'P:{pi?.DeclaringType?.FullName}.{pi?.Name}')]/summary"))
            .Configure((c, a) => { c.HasColumnAnnotation("Comment", GetCommentTextWithNewlineReplacement(a)); });
    }

    // adjust the documentation text to handle newline and whitespace
    private static string GetCommentTextWithNewlineReplacement(XmlNode a)
    {
        if (string.IsNullOrWhiteSpace(a.InnerText))
        {
            return null;
        }
        return string.Join(
            NewLinePlaceholder,
            a.InnerText.Trim()
                .Split(new string[] {"\r\n", "\r", "\n"}, StringSplitOptions.None)
                .Select(line => line.Trim()));
    }
}

在OnModelCreating方法中注冊約定。

預期結果：創建新遷移時，評論將作為注釋包含在內，例如

CreateTable(
    "schema.Table",
    c => new
        {
            Id = c.Decimal(nullable: false, precision: 10, scale: 0, identity: true,
                annotations: new Dictionary<string, AnnotationValues>
                {
                    { 
                        "Comment",
                        new AnnotationValues(oldValue: null, newValue: "Commenting the Id Column")
                    },
                }),
// ...

繼續第二部分：調整 SQL 生成器以從注釋創建評論。

這個是給Oracle的，不過MS Sql應該很相似

class CustomOracleSqlCodeGen : MigrationSqlGenerator
{
    // the actual SQL generator
    private readonly MigrationSqlGenerator _innerSqlGenerator;

    public CustomOracleSqlCodeGen(MigrationSqlGenerator innerSqlGenerator)
    {
        _innerSqlGenerator = innerSqlGenerator;
    }

    public override IEnumerable<MigrationStatement> Generate(IEnumerable<MigrationOperation> migrationOperations, string providerManifestToken)
    {
        var ms = _innerSqlGenerator.Generate(AddCommentSqlStatements(migrationOperations), providerManifestToken);

        return ms;
    }

    // generate additional SQL operations to produce comments
    IEnumerable<MigrationOperation> AddCommentSqlStatements(IEnumerable<MigrationOperation> migrationOperations)
    {
        foreach (var migrationOperation in migrationOperations)
        {
            // the original inputted operation
            yield return migrationOperation;

            // create additional operations to produce comments
            if (migrationOperation is CreateTableOperation cto)
            {
                foreach (var ctoAnnotation in cto.Annotations.Where(x => x.Key == "Comment"))
                {
                    if (ctoAnnotation.Value is string annotation)
                    {
                        var commentString = annotation.Replace(
                            CommentConvention.NewLinePlaceholder,
                            Environment.NewLine);

                        yield return new SqlOperation($"COMMENT ON TABLE {cto.Name} IS '{commentString}'");
                    }
                }

                foreach (var columnModel in cto.Columns)
                {
                    foreach (var columnModelAnnotation in columnModel.Annotations.Where(x => x.Key == "Comment"))
                    {
                        if (columnModelAnnotation.Value is AnnotationValues annotation)
                        {
                            var commentString = (annotation.NewValue as string)?.Replace(
                                CommentConvention.NewLinePlaceholder,
                                Environment.NewLine);

                            yield return new SqlOperation(
                                $"COMMENT ON COLUMN {cto.Name}.{columnModel.Name} IS '{commentString}'");
                        }
                    }
                }
            }
        }
    }
}

在DbMigrationsConfiguration構造函數中，注冊新的代碼生成器（同樣，這是 oracle 特定的，但與其他 SQL 提供程序類似）

internal sealed class Configuration : DbMigrationsConfiguration<EntityFramework.Dev.ZdbTestContext>
{
    public Configuration()
    {
        AutomaticMigrationsEnabled = false;
        var cg = GetSqlGenerator("Oracle.ManagedDataAccess.Client");
        SetSqlGenerator("Oracle.ManagedDataAccess.Client", new CustomOracleSqlCodeGen(cg));
    }
    // ...

預期結果：來自Up和Down方法的評論注釋被翻譯成 SQL 語句，這些語句改變了數據庫中的評論。

Answer 6

現在，在 2023 年，我已將 Mahmood Dehghan 提供的解決方案更新到 .Net 6 和 Entity Framework Core 6 here ，並進行了一些小修改，以包含來自基類 class 的屬性（如果主類中不存在），並向表中添加了擴展屬性。