Question

I am using ASP.NET MVC Razor And Data Annotation validators
My model:

public class Person 
{ 
    public int id { get; set; } 

    [Required] 
    public string FirstName { get; set; } 

    [Required] 
    public string LastName { get; set; } 
} 

FirstName And LastName are Requerd.
I want to Edit FirstName. My Methode is:

public ActionResult Edit([Bind(Include = "FirstName")]Person person)
{
    var p = GetPerson();
    if (TryUpdateModel(p))
    {
        //Save Changes;
    }
}

But TryUpdateModel always return false. because LastName is Invalid.

How Can I Prevent check Validation Of LastName in TryUpdateModel?

Note:

• The code is Simplified. my real code is very Complex
• I have To Use Requierd For Two Property
• I dont Want to use Different Model Class

Answer 1

I found Nice Solution. I must remove unused Field from ModelState. then ModelState.IsValid return true. first I need Create New Attribute class:

public class ValidateOnlyIncomingValuesAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        var modelState = filterContext.Controller.ViewData.ModelState;
        var valueProvider = filterContext.Controller.ValueProvider;

        var keysWithNoIncomingValue = modelState.Keys.Where( x=>!valueProvider.ContainsPrefix(x) );
        foreach (var key in keysWithNoIncomingValue)
            modelState[key].Errors.Clear();
    }
}

then I Add Attribute on my methode:

[ValidateOnlyIncomingValuesAttribute]
public ActionResult Edit([Bind(Include = "FirstName")]Person person)
{
    var p = GetPerson();
    if (ModelState.IsValid)
    {
        TryUpdateModel(p);
        //Save Changes;
    }
}

Look at this: http://blog.stevensanderson.com/2010/02/19/partial-validation-in-aspnet-mvc-2/