Call asp.net mvc Html Helper within custom html helper with expression parameter
- by Frank Michael Kraft
I am trying to write an html helper extension within the asp.net mvc framework.
public static MvcHtmlString PlatformNumericTextBoxFor<TModel>(this HtmlHelper instance, TModel model, Expression<Func<TModel,double>> selector)
where TModel : TableServiceEntity
{
var viewModel = new PlatformNumericTextBox();
var func = selector.Compile();
MemberExpression memExpession = (MemberExpression)selector.Body;
string name = memExpession.Member.Name;
var message = instance.ValidationMessageFor<TModel, double>(selector);
viewModel.name = name;
viewModel.value = func(model);
viewModel.validationMessage = String.Empty;
var result = instance.Partial(typeof(PlatformNumericTextBox).Name, viewModel);
return result;
}
The line
var message = instance.ValidationMessageFor<TModel, double>(selector);
has a syntax error. But I do not understand it. The error is: Fehler 2 "System.Web.Mvc.HtmlHelper" enthält keine Definition für "ValidationMessageFor", und die Überladung der optimalen Erweiterungsmethode "System.Web.Mvc.Html.ValidationExtensions.ValidationMessageFor(System.Web.Mvc.HtmlHelper, System.Linq.Expressions.Expression)" weist einige ungültige Argumente auf. C:\Projects\WorkstreamPlatform\WorkstreamPlatform_WebRole\Extensions\PlatformHtmlHelpersExtensions.cs 97 27 WorkstreamPlatform_WebRole
So according to the message, the parameter is invalid. But the method is actually declared like this:
public static MvcHtmlString ValidationMessageFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression);
So actually it should work.
