How can I use custom error messages with model binding in ASP.NET?

How can I use custom error messages with model binding in ASP.NET?

You can use data annotations like [Required] and specify the ErrorMessage property to customize error messages.

Can you give me an example of how to implement that?

Sure! For instance, you can create a model like this:

public class UserModel {
    [Required(ErrorMessage = "Username is required.")]
    public string Username { get; set; }
}

What if I want to validate multiple fields?

You can apply different attributes to each property. For example:

public class UserModel {
    [Required(ErrorMessage = "Username is required.")]
    public string Username { get; set; }

    [EmailAddress(ErrorMessage = "Invalid email format.")]
    public string Email { get; set; }
}

Is there a way to handle validation errors globally?

Yes, you can create a custom validation filter or middleware to handle errors globally and return custom responses.