How can I create a generic UniqueValidationAttribute in C# and DataAnnotation?

Question

I\'m trying to create a UniqueAttribute using the System.ComponentModel.DataAnnotations.ValidationAttribute

I want this to be generic as in I c

Answer 1

as @LBushkin mentioned, Attributes need compile time constants.

I would change your class from:

public class UniqueAttribute : ValidationAttribute

to:

public class UniqueAttribute : ValidationAttribute  
where T : DataContext{

    protected T Context { get; private set; }

  ...    

    }

and use it as:

[Required]
[StringLength(10)]
[Unique("Groups","name")]
public string name { get; set; }

This will help you inject a DataContext object, if needed, instead of creating an instance everytime

HTH

Edit: since an attribute cannot take a generic parameter, this could be another potential code:

public class UniqueAttribute : ValidationAttribute{

    public UniqueAttribute(Type dataContext, ...){
        if(dataContext.IsSubClassOf(typeof(DataContext))){
            var objDataContext = Activator.CreateInstance(dataContext);
        }
    }

}

and use it as:

[Required]
[StringLength(10)]
[Unique(typeof(DataContext), "Groups","name")]
public string name { get; set; }

HTH this time :)