Example code in C # that uses reflection and attribute simplification

Suppose there is now a student class (Student)

                                    {  {name = Age                    {;                     Address {;

If you need to determine if some fields (properties) are empty, or if they are greater than 0, the following code is available:

public static string Validatestudent (Student Student)        {            StringBuilder validatemessage = new StringBuilder ();                        if (string. IsNullOrEmpty (student. Name)            {                validatemessage.append ("cannot be empty");            }            if (string. IsNullOrEmpty (student. Sex)            {                validatemessage.append ("Gender cannot be empty");            }            if (student. Age <= 0)            {                validatemessage.append ("required is greater than 0");            }                        //...... Hundreds of lines                        //write here to find the wrong ah, if the required fields have more than 20, I would like to write it all the time!            return validatemessage.tostring ();        }

This kind of code, reusability is not high, and inefficient.

We can use attributes, reflection, and then traverse the properties and examine the attributes.

First, customize a "required" attribute class, inheriting from attribute

    <summary>    ///"required" feature, inherited from attribute    ///</summary> public sealed class Requireattribute: Attribute    {        private bool isrequire;        public bool Isrequire        {            get {return isrequire;}        }        <summary>///constructors///</summary>//        <param name= "Isrequire" ></param> Public        Requireattribute (bool isrequire)        {            this.isrequire = Isrequire;        }    }

Then use this custom attribute to mark the student class's member properties:

<summary>///Students///    </summary> public    class Student    {        //<summary> Name////        </summary>        private string name;        [Require (True)]        public string name        {            get {return Name;}            set {name = value;}        }        <summary>        ///Age        ///</summary> [Require (true)] public        int ages {get; set;}        <summary>        //        /Address        ///</summary> [Require (false)] public        string Address {get; set;} //        <summary>        //Gender        ///</summary> [Require (true)] public         string sex;    

To check the properties of a class by attributes:

  <summary>///check method, support generics///</summary>//<typeparam name= "T" ></typeparam >//<param name= "instance" ></param>//<returns></returns> public Stati                    C String Checkrequire<t> (T instance) {var validatemsg = new StringBuilder ();                        Gets the properties of the T class type T = typeof (T);                        var Propertyinfos = t.getproperties ();                Traversal property foreach (Var propertyInfo in Propertyinfos) {//check whether the attribute is marked by a property Requireattribute attribute = (requireattribute) attribute.getcustomattribute (PropertyInfo, typeof (Requireattribu                                TE));                No tag, skip directly if (attribute = = null) {continue; }//Gets the data type of the property var type = Propertyinfo.propertytYpe. ToString ().                                ToLower ();                                Gets the value of the attribute var = propertyinfo.getvalue (instance); if (type. Contains ("System.String")) {if (string. IsNullOrEmpty (String) value && attribute. Isrequire) Validatemsg.append (propertyinfo.name). Append ("Cannot be empty").                Append (","); } else if (type. Contains ("System.int")) {if ((int) value = = 0 && attribute. Isrequire) Validatemsg.append (propertyinfo.name). Append ("must be greater than 0").                Append (",");        }} return validatemsg.tostring (); }

Perform validation:

static void Main (string[] args)        {            var obj = new Student ()            {                Name = ""            };            Console.WriteLine (Checkrequire (obj));            Console.read ();        }

Result output:

Some people will find that sex also marks [Require (true)], why there is no authentication information, because sex does not implement the property {get; set;},getproperties is not available