How to customize the default error message "The value '' is invalid" for dynamically generated form

[fokwabest]

I am new to asp.net core. I have a form which is generated dynamically. I want the validation error message to be "The value must be numeric" instead I get
"The value 'a' is invalid" when I submit the form.

Here is my View Model:

[RegularExpression("^[0-9]*$", ErrorMessage = "The value must be numeric")]
public List<int> Units_Service { get; set; }

Here is my form code:

for (int i = 0; i < Model.Workload_Category_Name.Count; i++)

{

<div class="row">

<div class="col-md-3">

           <b><u>  @Html.DisplayFor(model => model.Workload_Category_Name[i])</u> </b>

       </div>

<div class="col-md-4">

@Html.TextBoxFor(model => model.Units_Service[i], new { style = "width: 15%", MaskedTextBox = "9999" })

          @Html.ValidationMessageFor(model => model.Units_Service[i])

       </div>

   </div>

 }

Despite the fact, I have put the custom error message in my View Model as shown above, I keep getting the default message "The value '' is invalid". Please what is the solution to this kind of scenario ?

 

[Skydiver]

Just looking at that, it seems wrong to be putting in a validator saying that a List<> must match a regular expression. I can see it for a single int, but not for a List<int>.

 

[Skydiver]

Check out the blog post below where FluentValidation is used to inspect the Strings which is a List<string>. You could potentially do something similar. My only doubt is that I don't know if FluentValidation can do client side validation.

Creating Complex Validation Rules Using Fluent Validation with ASP.NET Core

Read our blog

www.apress.com

 

[Skydiver]

If you don't want to go through the learning curve of yet another library, consider this other blog post where he hand builds the validation using the built in client side validators.

How to manually use the ASP.NET MVC's client side validation infrastructure - The Blinking Caret

ASP.NET MVC's client side validation is based on jQuery's validation plugin. Take advantage of this and enable validation on views without models.

www.blinkingcaret.com