还要谈谈Equals和GetHashcode

    [Serializable]
    public class Object
    {
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.MayFail)]
        public Object()
        {
        }
        public virtual string ToString()
        {
            return this.GetType().ToString();
        }
        [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
        public virtual bool Equals(object obj)
        {
            return RuntimeHelpers.Equals(this, obj);
        }
        [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
        public static bool Equals(object objA, object objB)
        {
            return objA == objB || (objA != null && objB != null && objA.Equals(objB));
        }
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success), TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
        public static bool ReferenceEquals(object objA, object objB)
        {
            return objA == objB;
        }
        [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
        public virtual int GetHashCode()
        {
            return RuntimeHelpers.GetHashCode(this);
        }
        [SecuritySafeCritical]
        [MethodImpl(MethodImplOptions.InternalCall)]
        public extern Type GetType();
        [ReliabilityContract(Consistency.WillNotCorruptState, Cer.Success)]
        protected virtual void Finalize()
        {
        }
        [SecuritySafeCritical]
        [MethodImpl(MethodImplOptions.InternalCall)]
        protected extern object MemberwiseClone();
        [SecurityCritical]
        private void FieldSetter(string typeName, string fieldName, object val)
        {
            FieldInfo fieldInfo = this.GetFieldInfo(typeName, fieldName);
            if (fieldInfo.IsInitOnly)
            {
                throw new FieldAccessException(Environment.GetResourceString("FieldAccess_InitOnly"));
            }
            Message.CoerceArg(val, fieldInfo.FieldType);
            fieldInfo.SetValue(this, val);
        }
        private void FieldGetter(string typeName, string fieldName, ref object val)
        {
            FieldInfo fieldInfo = this.GetFieldInfo(typeName, fieldName);
            val = fieldInfo.GetValue(this);
        }
        private FieldInfo GetFieldInfo(string typeName, string fieldName)
        {
            Type type = this.GetType();
            while (null != type && !type.FullName.Equals(typeName))
            {
                type = type.BaseType;
            }
            if (null == type)
            {
                throw new RemotingException(string.Format(CultureInfo.CurrentCulture, Environment.GetResourceString("Remoting_BadType"), new object[]
                {
                    typeName
                }));
            }
            FieldInfo field = type.GetField(fieldName, BindingFlags.IgnoreCase | BindingFlags.Instance | BindingFlags.Public);
            if (null == field)
            {
                throw new RemotingException(string.Format(CultureInfo.CurrentCulture, Environment.GetResourceString("Remoting_BadField"), new object[]
                {
                    fieldName, 
                    typeName
                }));
            }
            return field;
        }
    }

        public override int GetHashCode() {
            unsafe { 
                fixed (char *src = this) {
                    Contract.Assert(src[this.Length] == '\0', "src[this.Length] == '\\0'");
                    Contract.Assert( ((int)src)%4 == 0, "Managed string should start at 4 bytes boundary");
 
#if WIN32
                    int hash1 = (5381<<16) + 5381; 
#else 
                    int hash1 = 5381;
#endif 
                    int hash2 = hash1;

#if WIN32
                    // 32bit machines. 
                    int* pint = (int *)src;
                    int len = this.Length; 
                    while(len > 0) { 
                        hash1 = ((hash1 <<5) + hash1 + (hash1 >> 27)) ^ pint[0];
                        if( len <= 2) { 
                            break;
                        }
                        hash2 = ((hash2 <<5) + hash2 + (hash2 >> 27)) ^ pint[1];
                        pint += 2; 
                        len  -= 4;
                    } 
#else 
                    int     c;
                    char *s = src; 
                    while ((c = s[0]) != 0) {
                        hash1 = ((hash1 <<5) + hash1) ^ c;
                        c = s[1];
                        if (c == 0) 
                            break;
                        hash2 = ((hash2 <<5) + hash2) ^ c; 
                        s += 2; 
                    }
#endif 
#if DEBUG
                    // We want to ensure we can change our hash function daily.
                    // This is perfectly fine as long as you don't persist the
                    // value from GetHashCode to disk or count on String A 
                    // hashing before string B.  Those are bugs in your code.
                    hash1 ^= ThisAssembly.DailyBuildNumber; 
#endif 
                    return hash1 + (hash2 * 1566083941);
                } 
            }
        }

public struct Point {
   public int x;
   public int y; 

   //other methods

   public override int GetHashCode() {
      return x ^ y;
   }
}

public class Staff
    {
        private readonly string ID;
        private readonly string name;
 
        public Staff(string ID, string name)
        {
            this.ID = ID;
            this.name = name;
        }
 
        public override bool Equals(object obj)
        {
            if (obj == this)
                return true;
            if (!(obj is Staff))
                return false;
 
            var staff = (Staff)obj;
 
            return name == staff.name && ID == staff.ID;
        }
 
        public override int GetHashCode()
        {
            return (ID + name).GetHashCode();
        }
    }
 
    public class HashtableTest
    {
        public static void Main(){
 
            Staff a = new Staff("123", "langxue");
            Staff b = new Staff("123", "langxue");
 
            Console.WriteLine(a.Equals(b));
 
            var dic = new Dictionaryint>();
 
            dic.Add(new Staff("123", "langxue"), 0213);
 
            Console.WriteLine(dic.ContainsKey(new Staff("123", "langxue")));
        }
    }