How to pass parameters to a partial view in ASP.NET MVC?

make sure you add {} around Html.RenderPartial, as:

@{Html.RenderPartial("FullName", new { firstName = model.FirstName, lastName = model.LastName});}

not

@Html.RenderPartial("FullName", new { firstName = model.FirstName, lastName = model.LastName});

Use this overload (RenderPartialExtensions.RenderPartial on MSDN):

public static void RenderPartial(
    this HtmlHelper htmlHelper,
    string partialViewName,
    Object model
)

so:

@{Html.RenderPartial(
    "FullName",
    new { firstName = model.FirstName, lastName = model.LastName});
}

You need to create a view model. Something like this should do...

public class FullNameViewModel
{
     public string FirstName { get; set; }
     public string LastName { get; set; }

     public FullNameViewModel() { } 

     public FullNameViewModel(string firstName, string lastName)
     {
          this.FirstName = firstName;
          this.LastName = lastName;
     }

}

then from your action result pass the model

return View("FullName", new FullNameViewModel("John", "Doe"));

and you will be able to access @Model.FirstName and @Model.LastName accordingly.

Here is another way to do it if you want to use ViewData:

@Html.Partial("~/PathToYourView.cshtml", null, new ViewDataDictionary { { "VariableName", "some value" } })

And to retrieve the passed in values:

@{
    string valuePassedIn = this.ViewData.ContainsKey("VariableName") ? this.ViewData["VariableName"].ToString() : string.Empty;
}