Parameter and Parameter Property Validation

These validation attributes all have the same base class ValidationAttribute provided by System.ComponentModel.DataAnnotations namespace from either netfx or corefx.

Validation of Parameter Values

[HttpGet("webapi/user/GetById/{id}")]
ITask<HttpResponseMessage> GetByIdAsync(
    [Required, StringLength(10)] string id);

The id parameter is required and must be a string with a maximum length of 10 characters. Otherwise, a ValidationException will be thrown.

Validation of Parameter Property Values

public class UserInfo
{
    [Required]
    [StringLength(10, MinimumLength = 1)]
    public string Account { get; set; }

    [Required]
    [StringLength(10, MinimumLength = 6)]
    public string Password { get; set; }
}

[HttpPut("webapi/user/UpdateWithJson")]
ITask<UserInfo> UpdateWithJsonAsync(
    [JsonContent] UserInfo user);

When the user parameter is not null, it will validate its Account and Password properties. There is a UseParameterPropertyValidate property in HttpApiConfig that, when set to false, disables the validation of parameter property values.

Validation of Both

For the example in the previous section, if we also want to ensure that the user parameter value is not null, we can declare the method as follows:

[HttpPut("webapi/user/UpdateWithJson")]
ITask<UserInfo> UpdateWithJsonAsync(
    [Required, JsonContent] UserInfo user);