Mapping Enum from String

问题:

I have a string column in a database table which maps to an Enum in code. In my dbml file when I set the "Type" to MyTypes.EnumType I get the following error:

Error 1 DBML1005: Mapping between DbType 'VarChar(50) NOT NULL' and Type 'MyTypes.EnumType' in Column 'EnumCol' of Type 'Table1' is not supported.

This question: LINQ to SQL strings to enums indicates that what I am trying to do is possible, but how is it done?

回答1:

Curious - it should work IIRC; I'll see if I can do a quick example - however, you might want to check that you have the fully-qualified enum name (i.e. including the namespace).

[update] From here it seems that the RTM version shipped with a bug when resolving the enum. One workaround suggested (on that page) was to add the global:: prefix. It works fine for me without this workaround, so maybe it is fixed in 3.5 SP1? It also allegedly works fine in 3.5 if you use the unqualified name if the enum is in the same namespace.

[example] Yup, worked fine: with Northwind, I defined an enum for the shipping country:

namespace Foo.Bar
{
    public enum MyEnum
    {
        France,
        Belgium,
        Brazil,
        Switzerland
    }
}

I then edited the dbml to have:

<Column Name="ShipCountry" Type="Foo.Bar.MyEnum" DbType="NVarChar(15)" CanBeNull="true" />

This generated:

private Foo.Bar.MyEnum _ShipCountry;
//...
[Column(Storage="_ShipCountry", DbType="NVarChar(15)", CanBeNull=true)]
public Foo.Bar.MyEnum ShipCountry
{ get {...} set {...} }

And finally wrote a query:

using (DataClasses1DataContext ctx = new DataClasses1DataContext())
{
    var qry = from order in ctx.Orders
              where order.ShipCountry == Foo.Bar.MyEnum.Brazil
                || order.ShipCountry == Foo.Bar.MyEnum.Belgium
              select order;
    foreach (var order in qry.Take(10))
    {
        Console.WriteLine("{0}, {1}", order.OrderID, order.ShipCountry);
    }
}

Worked fine; results:

10250, Brazil
10252, Belgium
10253, Brazil
10256, Brazil
10261, Brazil
10287, Brazil
10290, Brazil
10291, Brazil
10292, Brazil
10299, Brazil

回答2:

I know this has been answered, but i'm still getting this error also. Very weird.

Anyways, I found a solution. You need to PREPEND the full namespace of the enum with global::

like WTF? Exactly. I know it sounds very weird. Here's an example screenie =>

alt text http://img11.imageshack.us/img11/7517/lolzqg.png

So lame :(

Anyways, I didn't figure this out. Some dude called Matt, did. And he posted a bug report on MS Connect and they can't repro it so it's not fixed, I guess.

Anyways, HTH.

回答3:

If you add the global:: qualyfier and press Control + space over the type in the designer.cs file it recognizes the type and you can remove it.