The default validation messages all end with a full stop and I want to remove this for every property validation message without having to add a custom ErrorMessage format for each validation attribute.

I've tried looking at setting methods in ModelBindingMessageProvider when adding Mvc as part of my Startup.cs class. No success with this...

CodePudding user response：

Yes, it is possible to remove the full stop from the default validation messages for all properties in your application without having to set a custom ErrorMessage format for each validation attribute.

Method 1

One way to achieve this is to create a custom validation attribute that inherits from the built-in validation attributes and overrides the FormatErrorMessage method. Here's an example of how you could create a custom RequiredAttribute that removes the full stop from the error message:

public class NoPeriodRequiredAttribute : RequiredAttribute
{
    public override string FormatErrorMessage(string name)
    {
        return base.FormatErrorMessage(name).TrimEnd('.');
    }
}

You can then use this custom attribute instead of the built-in RequiredAttribute in your model properties:

public class MyModel
{
    [NoPeriodRequired]
    public string Name { get; set; }
}

You can apply the same concept to any other built-in validation attributes, such as StringLengthAttribute, RangeAttribute, etc.

Method 2

There isn't a built-in method that allows you to globally remove the full stop from validation error messages in the way you described.

However, one approach you could take to achieve a similar result without creating a custom validation attribute is to use a custom ErrorMessageProvider and change the way the validation error messages are generated. An ErrorMessageProvider is an interface that is responsible for generating the error message for a validation error. By implementing your own ErrorMessageProvider and registering it with the framework, you can change the default behavior of the validation system and remove the full stop from the error messages.

Here's an example of a custom ErrorMessageProvider that removes the full stop from the error message:

public class NoPeriodErrorMessageProvider : IErrorMessageProvider
{
    public string GetErrorMessage(ModelError error)
    {
        return error.ErrorMessage.TrimEnd('.');
    }
}

You can register this custom ErrorMessageProvider in the Startup.cs file in the ConfigureServices method like this:

services.AddSingleton<IErrorMessageProvider>(new NoPeriodErrorMessageProvider());

Keep in mind this will change the default messages globally, but it will not change the messages in resource files.

It's also important to note that this approach, while it will remove the period from all error messages, it will also affect custom error messages that you might set in your validation attributes.

Keep in mind that this approach is not compatible with all frameworks, but only specific ones that uses the IErrorMessageProvider interface.

CodePudding user response：

The error message is from ModelError in the ModelState but they don't have set method so can't override the error message template(as I know) so I have 2 ways to do it, first method is assign a new ModelError and add assign you own error message, second one is almost same as first one but you can keep the filed name in error message.

Method 1

builder.Services.Configure<ApiBehaviorOptions>(options =>
{
    options.InvalidModelStateResponseFactory = (actionContext) =>
    {
        foreach (var x in actionContext.ModelState)
        {
            for (var i = 0; i < x.Value.Errors.Count; i  )
            {
                x.Value.Errors[i] = new Microsoft.AspNetCore.Mvc.ModelBinding.ModelError("Your message here");
            }
        }

        var problemDetails = new ValidationProblemDetails(actionContext.ModelState);

        problemDetails.Type = options.ClientErrorMapping[400].Link;
        problemDetails.Title = "One or more validation errors occurred.";
        problemDetails.Status = StatusCodes.Status400BadRequest;

        return new BadRequestObjectResult(problemDetails);
    };
});

Method 2

builder.Services.Configure<ApiBehaviorOptions>(options =>
{
    options.InvalidModelStateResponseFactory = (actionContext) =>
    {
        var errorDictionary = new Dictionary<string, string[]>(StringComparer.Ordinal);
        var errorMessageTemplate = "Your message here, The field {0} is required";
        foreach (var keyModelStatePair in actionContext.ModelState)
        {
            var key = keyModelStatePair.Key;
            var errors = keyModelStatePair.Value.Errors;
            if (errors != null && errors.Count > 0)
            {
                if (errors.Count == 1)
                {
                    var errorMessage = errorMessageTemplate;
                    errorDictionary.Add(key, new[] { string.Format(errorMessage, key) });
                }
                else
                {
                    var errorMessages = new string[errors.Count];
                    for (var i = 0; i < errors.Count; i  )
                    {
                        errorMessages[i] = errorMessageTemplate;
                    }

                    errorDictionary.Add(key, errorMessages);
                }
            }
        }

        var errorModel = new
        {
            Type = options.ClientErrorMapping[400].Link,
            Title = "One or more validation errors occurred.",
            Status = StatusCodes.Status400BadRequest,
            Errors = errorDictionary
        };
        return new BadRequestObjectResult(errorModel);
    };
});