Asp.net-mvc – ValidationMessage – Handle multiple errors for the same property

asp.net-mvc

I'm using ValidationMessage control in MVC. When validating each property, it may have more than one error message to show, but the ValidationMessage only displays the first error message in the list.

Here is an example:

ModelState["Key"] = new ModelState();
ModelState["Key"].Errors.Add("Error 1");
ModelState["Key"].Errors.Add("Error 2");

and in the html I have: <%= Html.ValidationMessage("Key")%>

which displays: "Error 1"

I want to see all error messages on the page which will be "Error 1 Error 2"

Any idea how to do it?

Best Solution

I had exactly the same problem, so I created an extension method for HtmlHelper as replacement for the MVC ValidationMessage method.

The benefit of this over ValidationSummary method is that it displays error message per field so you can place it right next to each field (same as ValidationMessage method).

public static string AllValidationMessage(this HtmlHelper helper, string modelName)
{
    StringBuilder builder = new StringBuilder();
    TagBuilder ulTag = new TagBuilder("ul");
    ulTag.AddCssClass("u-error-list");

    builder.Append(ulTag.ToString(TagRenderMode.StartTag));
    if (helper.ViewData.ModelState.ContainsKey(modelName) &&
        helper.ViewData.ModelState[modelName].Errors.Count > 0)
    {
        foreach (var err in helper.ViewData.ModelState[modelName].Errors)
        {
            TagBuilder liTag = new TagBuilder("li") { InnerHtml = HttpUtility.HtmlEncode(err.ErrorMessage) };
            liTag.AddCssClass("u-error-item");
            builder.Append(liTag.ToString());
        }
    }
    builder.Append(ulTag.ToString(TagRenderMode.EndTag));

    var msgSpan = helper.ValidationMessage(modelName, "{placeholder}");

    if (msgSpan == null)
        return string.Empty;

    return msgSpan.ToHtmlString().Replace("{placeholder}", builder.ToString());
}

public static string AllValidationMessageFor<TModel, TProperty>(this HtmlHelper<TModel> helper, Expression<Func<TModel, TProperty>> expression)
{
    return HtmlHelperExtensions.AllValidationMessage(helper, ExpressionHelper.GetExpressionText(expression));
}

Edit: added AllValidationMessageFor method
Edit: added a null check on msgSpan

Related Solutions

C# – How to handle multiple submit buttons in ASP.NET MVC Framework

Here is a mostly clean attribute-based solution to the multiple submit button issue based heavily on the post and comments from Maarten Balliauw.

[AttributeUsage(AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public class MultipleButtonAttribute : ActionNameSelectorAttribute
{
    public string Name { get; set; }
    public string Argument { get; set; }

    public override bool IsValidName(ControllerContext controllerContext, string actionName, MethodInfo methodInfo)
    {
        var isValidName = false;
        var keyValue = string.Format("{0}:{1}", Name, Argument);
        var value = controllerContext.Controller.ValueProvider.GetValue(keyValue);

        if (value != null)
        {
            controllerContext.Controller.ControllerContext.RouteData.Values[Name] = Argument;
            isValidName = true;
        }

        return isValidName;
    }
}

razor:

<form action="" method="post">
 <input type="submit" value="Save" name="action:Save" />
 <input type="submit" value="Cancel" name="action:Cancel" />
</form>

and controller:

[HttpPost]
[MultipleButton(Name = "action", Argument = "Save")]
public ActionResult Save(MessageModel mm) { ... }

[HttpPost]
[MultipleButton(Name = "action", Argument = "Cancel")]
public ActionResult Cancel(MessageModel mm) { ... }

Update: Razor pages looks to provide the same functionality out of the box. For new development, it may be preferable.

Asp.net-mvc – the ‘page lifecycle’ of an ASP.NET MVC page, compared to ASP.NET WebForms

I'll attempt to comment on each of the bullet points you mentioned:

Your master pages still exist in MVC and are used to provide a consistent layout to the site. not much new there.

Your content pages will become views in the MVC world. They still provide the same content areas to your master pages.

The eventhandling of webforms should not be used in MVC, instead your Controller classes and their action methods will handle loading your data into a "model" that gets passed to the view.

Although webform style databinding is possible in MVC, I find that it is not the optimal solution. Better to place your data in a model class and strongly type your view so that you have direct access to that model. Then its simply a matter of using the <%= ViewData.Model.SomeProperty %> syntax to access your data and display it in the desired locations. As for viewstate, my recommendation is to forget that it even exists.

Remember that one of the advantages of using MVC is that you have control over the HTML you send to the client. Embrace that power and try to find solutions that allow you to maintain that control. Webform controls attempt to hide the the html from you and as such make it more difficult to customize the html when you need to.

I would highly recommend JQuery or one of the other similarly powerful javascript libraries. But learn to use them to access the HTML DOM directly and avoid the id mangling issues of webform controls.

You can use jquery to hook into the dropdown selection on the client side and submit standard or ajax style requests. Those request can return new pages, redirects, html fragments or even JSON data that can be used to update the existing page.

The asp.net Session can be used as needed.

Best Solution

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C# – How to handle multiple submit buttons in ASP.NET MVC Framework

Asp.net-mvc – the ‘page lifecycle’ of an ASP.NET MVC page, compared to ASP.NET WebForms

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