How to Add a read-only Property to Database first Entity Framework 6 metadata

Question

How to Add a read-only Property to Database first Entity Framework 6 metadata

asp.net asp.net-mvc c# entity-framework-6

Question

i'm learning MVC and EF6 on my own, actually i'm following the tutorials on asp.net site that are very helpful. Today i was following this tutorial. This is with code-first approach, but i'm doing this with database first approach. so i've followed the instructions to add the following read-only property to the Model, in my case to the model's metadata.

[Display(Name = "Full Name")]
public string FullName
{
      get
      {
         return LastName + ", " + FirstMidName;
      }
}

but when i try to Access the students page i got this error:

An exception of type 'System.InvalidOperationException' occurred in System.ComponentModel.DataAnnotations.dll but was not handled in user code. Additional information: The associated metadata type for type 'MVCEF6DBFirst.Models.Student' contains the following unknown properties or fields: FullName. Ensure that the names of these members match the names of the properties of the main type.

I know that there is an error with the property recently added so i googled it but i can't find a correct solution to this.

Could you tell me how i should add this property to my model

thanks in advance.

DigitalDNA

Popular Answer

As i commented in the @sergik's answer i've found another approach to get this work (based on @sergik's answer).

EF Model Class



public class StudentMetadata
{                

}

Declare a partial class



[MetadataType(typeof(StudentMetadata))]    
    public partial class Student    
    {    
       [Display(Name = "Full Name")]    
       public string FullName    
       {    
          get    
          {    
             return LastName + ", " + FirstName;    
          }    
       }    
    }

add DataAnnotations reference to this class



    using System.ComponentModel.DataAnnotations;

Run Project. This is the result

Both @Sergik's and me answers were tested and both Works well.

Hope to be useful for other people.

DigitalDNA

View more on Stack Overflow

sergik · Accepted Answer · 9/5/2014 6:35:28 AM

If the FullName column doesn't exist in the database table which means no property FullName exists in your EF model Student class you'll get this error.

I doubt you can achieve what you want using metadata-approach. But you can modify the way your properties are rendered in a view. If the following is your EF model class:
```
public partial class Student
{   
  public string FullName 
  {             
    get;
    set;
  }
}
```

Then create another partial class called Student and place it in the same assembly(folder) but in a different file with a different file name. it'd look like this:

[MetadataType(typeof(StudentMetadata))]
public partial class Student
{
}

public class StudentMetadata
{
    [Display(Name = "Full Name")]
    public string FullName { get; set; }          
}

then if you render your EF model Student class in a view

@model Models.Student
@Html.DisplayForModel()

The name of the property will be displayed the way you wanted:

If you want to prevent user from editing the field by making it readonly, you may want to use this

 @Html.TextBoxFor(m => m.FullName, new{ disabled = "disabled", @readonly = "readonly" })

I am not sure how to achieve the same effect with Html.EditorForModel

Alternatively if you still want a property FullName made up of other two properties FirstName and LastName I'd try:

Your EF model class:

public partial class Student
{
 public string FirstName
 {
     get; set;
 }

 public string SecondName
 {
    get; set;
 }

}

Class extending Student class:

public class StudentChild : Student
{

[Display(Name="User name")]
public String FullName
{
    get { return FirstName + ", " + SecondName; }
}

}

Then in your view:

@model StudentChild

@Html.DisplayForModel()

I am not sure the latter is the perfect approach as in the case that your underlying database schema changes then you need to modify your child class.

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