Get Label for Expresssion Func<T, U> Only Works for String Type
I have a function that takes an Expression< Func < TModel, Object >> which I want to get the DisplayName from the metadata in the model. This works only for expressions with a signature of having Func< TModel,String> . Func< TModel,Int> or Func< TModel,DateTime> fails with the following error.
Templates can be used only with field access, property access, single-dimension array index, or single-parameter custom indexer expressions.
Example Metadata Class with a few properties
This is a sample Metadata class that supplies the DisplayAttribute for a few properties.
public class TestMetadata
{
[Display(Name = "Area")]
public Object Description { get; set; }
[Display(Name = "Date Property")]
public Object Date { get; set; }
[Display(Name = "Int Property")]
public Object Length { get; set; }
}
Function to Extract DisplayAttribute Name Property
This function works fine for the return values of string (Example CustomDisplayFor(Html,m => m.Description) returns the value "Area" as expected). However, fails with the noted error in the following circumstances.
public static String CustomDisplayFor<TModel>(HtmlHelper<TModel> html,
Expression<Func<TModel, Object>> func)
{
return html.LabelFor(func);
}
Is there a way I can get the DisplayAttribute information from these other types of properties?
Okay, I figured out that this works when you add another Type Reference for the return value.
The Signature Becomes
public static String CustomDisplayFor<TModel,TResult>(HtmlHelper<TModel> html,
Expression<Func<TModel, TResult>> func)
{
return html.LabelFor(func);
}
Calling Code is the Same
CustomDisplayFor(Html,m => m.Date) // This now works => "Date Property" returned
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