Set error message for validation of non-nullable types
I use ASP.NET core 3.1
I have:
class A { public int A {get;set;} } When I send json model {"A": null} I get "error": "INVALID". But I wait "REQUIRED".
I tried do as written above, but it doesn’t work.
options.ModelBindingMessageProvider.SetValueMustNotBeNullAccessor( _ => "The field is required."); How can I customize the message?
as a trick, you could use the special field as string and cast it in receiver place!
Do you mean you cannot get the error message in controller?Here is a worked demo:
TestInt:
public class TestInt { public int a { get; set; } public string b { get; set; } } Controller:
[AcceptVerbs("GET")] public ActionResult CheckA() { return View(); } [AcceptVerbs("POST")] public ActionResult CheckA(TestInt testInt) { if (!ModelState.IsValid) { StringBuilder result = new StringBuilder(); foreach (var item in ModelState) { string key = item.Key; var errors = item.Value.Errors; foreach (var error in errors) { result.Append(key + " " + error.ErrorMessage); } } TempData["Errors"] = result.ToString(); } return View(); } View:
<div class="row"> <div class="col-md-4"> <form method="post"> <div asp-validation-summary="ModelOnly" class="text-danger"></div> <div class="form-group"> <label asp-for="a" class="control-label"></label> <input asp-for="a" class="form-control" /> <span asp-validation-for="a" class="text-danger"></span> </div> <div class="form-group"> <label asp-for="b" class="control-label"></label> <input asp-for="b" class="form-control" /> <span asp-validation-for="b" class="text-danger"></span> </div> <div class="form-group"> <input type="submit" value="Test" class="btn btn-primary" /> </div> </form> </div> </div> startup.cs:
services.AddControllers() .AddMvcOptions(options => { options.ModelBindingMessageProvider.SetValueMustNotBeNullAccessor( _ => "REQUIRED"); }); result： 
