[英]Entity Framework - how to join tables without LINQ and with only string?
我对实体框架有疑问。 如果您知道答案,请回答。 我有这样的查询:
String queryRaw =
"SELECT " +
"p.ProductName AS ProductName " +
"FROM ProductEntities.Products AS p " +
"INNER JOIN CategoryEntities.Categories AS c " +
"ON p.CategoryID = c.CategoryID ";
ObjectQuery<DbDataRecord> query = new ObjectQuery<DbDataRecord>(queryRaw, entityContext);
GridView1.DataSource = query;
GridView1.DataBind();
特别是我想在一个查询中加入几个表,但是我不能使用LINQ,也不能将ObjectQuery与映射到查询中DB字段的对象一起使用。 因为每个实体都是动态创建的。 所以这就是我不能使用的:
msdn.microsoft.com/zh-CN/library/bb425822.aspx#linqtosql_topic12
msdn.microsoft.com/zh-CN/library/bb896339%28v=VS.90%29.aspx
问题是我可以使用类似这样的东西而不使用对象吗?
query.Join ("INNER JOIN CategoryEntities.Category ON p.CategoryID = c.CategoryID ");
目的是使用ObjectQuery的Join方法和语法,如Where方法:
msdn.microsoft.com/zh-CN/library/bb338811%28v=VS.90%29.aspx
谢谢阿特姆
我现在看到的任何决定是将ObjectQuery临时转换为字符串,将连接表添加为字符串,然后将其转换回ObjectQuery:
RoutesEntities routesModel = new RoutesEntities(entityConnection);
String queryRaw = "SELECT " +
"rs.RouteID AS RouteID, " +
"rs.LocaleID AS LocaleID, " +
"rs.IsSystem AS IsSystem " +
"FROM RoutesEntities.Routes AS rs ";
_queryData = new ObjectQuery<DbDataRecord>(queryRaw, routesModel);
var queryJoin = _queryData.CommandText + " INNER JOIN LocalesEntities.Locales AS ls ON ls.LocaleID = rs.LocaleID ";
_queryData = new ObjectQuery<DbDataRecord>(queryJoin, routesModel);
也许有人有更一致的建议?
最终,我找到了一个更好的解决方案,我们可以在主查询中使用子查询。 例如 :
var db = CustomEntity();
ObjectQuery<Categories> query1 = db.Categories.Where("it.CategoryName='Demo'").Select ("it.CategoryID");
var categorySQL = query1.ToTraceString().Replace("dbo", "CustomEntity"); // E-SQL need this syntax
ObjectQuery<Products> query2 = db.Categories.Where("it.CategoryID = (" + categorySQL + ")");
一些例子在这里:
http://msdn.microsoft.com/en-us/library/bb896238.aspx
祝好运!
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