How do you do web forms model validation?

问题

We have an application with three layers: UI, Business, and Data. The data layer houses Entity Framework v4 and auto-generates our entity objects. I have created a buddy class for the entity VendorInfo:

namespace Company.DataAccess
{
    [MetadataType(typeof(VendorInfoMetadata))]
    public partial class VendorInfo
    {
    }

    public class VendorInfoMetadata
    {
        [Required]
        public string Title;

        [Required]
        public string Link;

        [Required]
        public string LinkText;

        [Required]
        public string Description;
    }
}

I want this validation to bubble up to the UI, including custom validation messages assigned to them. In MVC this is a piece of cake but in web forms I have no clue where to begin. What is the best way to utilize model validation in asp.net web forms?

I did find an article that explains how to build a server control for it, but I can't seem to get it working. It compiles and even recognizes the control but I can never get it to fire.

Any ideas?

Thanks everyone.

回答1:

I solved it. It would appear that the server control I found was not designed to read fields in a buddy class via the MetadataType attribute. I modified the code to look for its validation attributes in the buddy class rather than the entity class itself.

Here is the modified version of the linked server control:

    [DefaultProperty("Text")]
    [ToolboxData("<{0}:DataAnnotationValidator runat=server></{0}:DataAnnotationValidator>")]
    public class DataAnnotationValidator : BaseValidator
    {
        #region Properties

        /// <summary>
        /// The type of the source to check
        /// </summary>
        public string SourceTypeName { get; set; }

        /// <summary>
        /// The property that is annotated
        /// </summary>
        public string PropertyName { get; set; }

        #endregion

        #region Methods

        protected override bool EvaluateIsValid()
        {
            // get the type that we are going to validate
            Type source = GetValidatedType();

            // get the property to validate
            FieldInfo property = GetValidatedProperty(source);

            // get the control validation value
            string value = GetControlValidationValue(ControlToValidate);

            foreach (var attribute in property.GetCustomAttributes(
                     typeof(ValidationAttribute), true)
                       .OfType<ValidationAttribute>())
            {
                if (!attribute.IsValid(value))
                {
                    ErrorMessage = attribute.ErrorMessage;
                    return false;
                }
            }
            return true;
        }

        private Type GetValidatedType()
        {
            if (string.IsNullOrEmpty(SourceTypeName))
            {
                throw new InvalidOperationException(
                  "Null SourceTypeName can't be validated");
            }

            Type validatedType = Type.GetType(SourceTypeName);
            if (validatedType == null)
            {
                throw new InvalidOperationException(
                    string.Format("{0}:{1}",
                      "Invalid SourceTypeName", SourceTypeName));
            }

            IEnumerable<MetadataTypeAttribute> mt = validatedType.GetCustomAttributes(typeof(MetadataTypeAttribute), false).OfType<MetadataTypeAttribute>();
            if (mt.Count() > 0)
            {
                validatedType = mt.First().MetadataClassType;
            }

            return validatedType;
        }

        private FieldInfo GetValidatedProperty(Type source)
        {
            FieldInfo field = source.GetField(PropertyName);
            if (field == null)
            {
                throw new InvalidOperationException(
                  string.Format("{0}:{1}",
                    "Validated Property Does Not Exists", PropertyName));
            }
            return field;
        }

        #endregion
    }

This code only looks in the buddy class. If you want it to check an actual class and then its buddy class, you'll have to modify it accordingly. I did not bother doing that because usually if you are using a buddy class for validation attributes it's because you are not able to use the attributes in the main entity class (e.g. Entity Framework).

回答2:

For model validation in web forms I'm using DAValidation library. It supports validation on client side (including unobtrusive validation), extensibility based on same principles as in MVC. It is MS-PL licensed and available via Nuget.

And here is bit out of date article describing with what thoughts control was build.

来源：https://stackoverflow.com/questions/5600707/how-do-you-do-web-forms-model-validation