C＃SQLite'约束失败'

Question

I have a BindingList which is the DataSource of a DataGridView. I want to be able to use SqliteDataAdapter + SqliteCommandBuilder to simplify loading/saving to my Sqlite database, but because SqliteDataAdapter.Fill/Update both only take a DataTable or DataSet as a parameter, I am using extension methods to convert my BindingList to/from a DataTable.

When doing this, if I update some values in my BindingList, then try to update the DB, I am getting UNIQUE constraint failed exceptions. I am not really sure why my SqliteDataAdapter is trying to execute INSERTs and not updates, considering no values have been added, only updated.

I could DELETE * from the table before calling adapter.Update, but that doesn't seem ideal or correct.

What is the proper way to achieve my goal (being able to use adapter.Fill/Update with a generic list)?

public void LoadDatabase()
{
    using (var conn = new SQLiteConnection(dbConnectionString))
    {
        using (var adapter = new SQLiteDataAdapter("SELECT * FROM proxies", conn))
        {
            var table = new DataTable();
            adapter.Fill(table);
            var list = new BindingList<Proxy>(table.ConvertTo<Proxy>());
            foreach (var item in list)
            {
                proxies.Add(item);
            }
        }
    }
}

public void SaveDatabase()
{
    using (var conn = new SQLiteConnection(dbConnectionString))
    {
        using (var adapter = new SQLiteDataAdapter("SELECT * FROM proxies", conn))
        {
            using (var builder = new SQLiteCommandBuilder(adapter))
            {
                adapter.InsertCommand = builder.GetInsertCommand();
                adapter.DeleteCommand = builder.GetDeleteCommand();
                adapter.UpdateCommand = builder.GetUpdateCommand();
                var table = proxies.ToDataTable();
                adapter.Update(table);

            }
        }
    }
}

Extension methods used:

public static List<T> ConvertTo<T>(this DataTable datatable) where T : new()
{
    List<T> Temp = new List<T>();
    try
    {
        List<string> columnsNames = new List<string>();
        foreach (DataColumn DataColumn in datatable.Columns)
            columnsNames.Add(DataColumn.ColumnName);
        Temp = datatable.AsEnumerable().ToList().ConvertAll<T>(row => getObject<T>(row, columnsNames));
        return Temp;
    }
    catch
    {
        return Temp;
    }

}
public static T getObject<T>(DataRow row, List<string> columnsName) where T : new()
{
    T obj = new T();
    try
    {
        string columnname = "";
        string value = "";
        PropertyInfo[] Properties;
        Properties = typeof(T).GetProperties();
        foreach (PropertyInfo objProperty in Properties)
        {
            columnname = columnsName.Find(name => name.ToLower() == objProperty.Name.ToLower());
            if (!string.IsNullOrEmpty(columnname))
            {
                value = row[columnname].ToString();
                if (!string.IsNullOrEmpty(value))
                {
                    if (objProperty.PropertyType.IsEnum)
                    {
                        objProperty.SetValue(obj, Enum.Parse(objProperty.PropertyType, value));
                    }
                    else
                    {
                        if (Nullable.GetUnderlyingType(objProperty.PropertyType) != null)
                        {
                            value = row[columnname].ToString().Replace("$", "").Replace(",", "");
                            objProperty.SetValue(obj, Convert.ChangeType(value, Type.GetType(Nullable.GetUnderlyingType(objProperty.PropertyType).ToString())), null);
                        }
                        else
                        {
                            value = row[columnname].ToString().Replace("%", "");
                            objProperty.SetValue(obj, Convert.ChangeType(value, Type.GetType(objProperty.PropertyType.ToString())), null);
                        }
                    }
                }
            }
        }
        return obj;
    }
    catch
    {
        return obj;
    }
}

public static DataTable ToDataTable<T>(this IList<T> data)
{
    PropertyDescriptorCollection properties =
        TypeDescriptor.GetProperties(typeof(T));
    DataTable table = new DataTable();
    foreach (PropertyDescriptor prop in properties)
        table.Columns.Add(prop.Name, Nullable.GetUnderlyingType(prop.PropertyType) ?? prop.PropertyType);
    foreach (T item in data)
    {
        DataRow row = table.NewRow();
        foreach (PropertyDescriptor prop in properties)
            row[prop.Name] = prop.GetValue(item) ?? DBNull.Value;
        table.Rows.Add(row);
    }
    return table;
}

Answer 1

I decided to just delete all records before executing adapter.Update(), it is the simplest solution I've been able to think of. If anyone has a better idea, do tell.

public void SaveDatabase()
{
    using (var conn = new SQLiteConnection(dbConnectionString))
    {
        using (var adapter = new SQLiteDataAdapter("SELECT * FROM proxies", conn))
        {
            using (var builder = new SQLiteCommandBuilder(adapter))
            {
                conn.Open();
                using (var cmd = new SQLiteCommand("DELETE FROM proxies", conn))
                {
                    cmd.ExecuteNonQuery();
                }
                adapter.InsertCommand = builder.GetInsertCommand();
                adapter.DeleteCommand = builder.GetDeleteCommand();
                adapter.UpdateCommand = builder.GetUpdateCommand();
                var table = proxies.ToDataTable();
                adapter.Update(table);

            }
        }
    }
}