如何加载EF类及其关系类

Question

I have two tables:

MY_TABLE
ID   CODE  VERSION  DESCRIPTION
1    AAA   1        A Test

MY_CHILD_TABLE
ID   CODE  VERSION  COLOR
1    AAA   1        Blue

Both are included in my EF model and there is a navigation property setup on both tables.

Now I have the following class to get the data:

public static MyData GetMyData(string Code, string version)
{
    using (var context = new Entities())
    {
        return context.MY_TABLE.Where(x => x.MY_CODE == Code && x.MY_VERSION == version).FirstOrDefault();
    }
} 

This is fine if I want just the data for MY_TABLE. However I now have a scenario where I want both MY_TABLE and MY_CHILD_TABLE data returned.

How can I return that information back?
ie I want to be able to something to the effect of:

var result = MyClass.GetMyData("aaa",1);
var color = result.NAV_PROP.Color;

If I understand correctly this doesn't work because I am closing the context in the GetMyData method.

Answer 1

如果您具有导航属性，只需包括它们：

return context.MY_TABLE.Include(x=>x.MY_CHILD_TABLEProperty).Where(x => x.MY_CODE == Code && x.MY_VERSION == version).FirstOrDefault();

Answer 2

There are two ways to do that, once you have lazyloading enabled (which is the default setting on EF).

1) Use the extension "Include"

context.Table.Include(t => t.RelatedTable).Where(x => ..Condition..).FirstOrDefault();

If your relationship is configured to be a "Required" foreign key relationship, EF will understand you're doing a "Inner Join"

If your relationship is configured to be a "Nullable" (not required), EF will understand you're doing a "Left Join".

2) Select the related data using a .Select before the data is enumerated.

context.Table.Where(x = ..Conditions..).Select(s => 
     new { 
          RelatedTableColumn = s.RelatedTable.Column 
          ...
     }).FirstOrDefault();

On this case EF will understand you're doing a "Inner Join" like using "Include", but, it will only return your "Selected" columns, which results in better performance for bigger queries.

Edit 1

Ps*: If you can't access ".Include" extension, just add:

 using System.Data.Entity;