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How to pass a System.Type into a generic method using reflection [duplicate]

开发者 https://www.devze.com 2023-04-06 09:17 出处:网络
This question already has answers here: C开发者_如何学JAVAlosed 11 years ago. Possible Duplicate:
This question already has answers here: C开发者_如何学JAVAlosed 11 years ago.

Possible Duplicate:

How to use reflection to call generic Method?

I'm trying to simplify some EF Code First configuration.

Instead of writing code like this:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Asset>().ToTable("Assets");
    modelBuilder.Entity<VideoAsset>().ToTable("VideoAssets");
    modelBuilder.Entity<ImageAsset>().ToTable("ImageAssets");
    ...
}

I'm wrapping the table per type declaration into a class and using reflection to call the modelBuilder

public class TablePerTypeBuilder<TBase> where TBase : class
{
    public void Build(DbModelBuilder modelBuilder)
    {
        //modelBuilder.Entity<Asset>().ToTable("Assets");
        modelBuilder.Entity<TBase>().ToTable(typeof(TBase).Name);

        //modelBuilder.Entity<VideoAsset>().ToTable("VideoAssets");
        //modelBuilder.Entity<ImageAsset>().ToTable("ImageAssets");
        var types = from a in AppDomain.CurrentDomain.GetAssemblies()
                    from t in a.GetTypes()
                    where typeof(TBase).IsAssignableFrom(t)
                    select t;

        foreach (Type type in types)
        {           
            modelBuilder.Entity<type>().ToTable(type.Name); 
            //Error - The type or namespace name 'type' could not be found (are you missing a using directive or an assembly reference?)
        }
    }
}

It's not possible to add a Type as a generic parameter due to compile time safety. So is it possible to make same call using refection?

The aim is to call the builder like

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    TablePerTypeBuilder<Asset> builder = new TablePerTypeBuilder<Asset>();
    builder.Build(modelBuilder);
}


As suggested, you can use MakeGenericMethod(). But its a lot of ugly typing like that:

var method = modelBuilder.GetType().GetMethod("Entity");
var genericMethod = method.MakeGenericMethod(type);
var entTypConfig = genericMethod.Invoke(modelBuilder, null);
entTypConfig.GetType()
    .InvokeMember("ToTable", BindingFlags.InvokeMethod, null, entTypConfig, 
                  new object[] {type.Name});


You could build an expression and compile it down into a delegate:

public void Build(DbModelBuilder builder) 
{
  // Stuff

  var param = Expression.Parameter(typeof(DbModelBuilder));
  foreach (var type in types)
  {
    var method = Expression.Call(
      Expression.Constant(this),      // Call to self.
      "BuildInternal",                // The method to call.
      new[] { type },                 // The generic arguments.
      param);                        // The parameters.

    Expression.Lambda(method, param).Compile().DynamicInvoke(builder);
  }
}

Which when executed could call:

public void BuildInternal<T>(DbModelBuilder builder) where T : class
{
  builder.Entity<T>.ToTable(typeof(T).Name);
}
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