C#如何查找ArrayList 中的某个数据？(附解决方案及源码)

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请问，如何查找ArrayList 中的某个数据？？？
我下面的代码为何总是返回false?
难道一定要用循环吗？

private void button1_Click(object sender, EventArgs e)
{

ArrayList SenderAddressAL= new ArrayList();

SenderAddressAL.Add(new SenderAddress("[Use system default]", ""));
SenderAddressAL.Add(new SenderAddress("abc@ebay.com", "abc@ebay.com"));

            if (SenderAddressAL.Contains(new SenderAddress("abc@ebay.com", "abc@ebay.com")))
                    MessageBox.Show("Have");
            else
                    MessageBox.Show("NOT Have");

}

public class SenderAddress
{
//-----Description-----

protected string description;

        public string Description
        {
            get { return description; }

set { description = value; }
}

//-----eMailAddress-----

protected string emailaddress;

        public string eMailAddress
        {
            get { return emailaddress.ToLower(); }

set { emailaddress = value; }
}

        public SenderAddress(string descr, string emailaddr)
        {
            description = descr;
            emailaddress = emailaddr;
        }
    }

Solution:

SenderAddress override Equals

参考这个代码，把类改一下就可以了：

//可以比较的类
class A
{
private int m_i;
public A(int i)
{
  this.m_i = i;
}
public override bool Equals(object obj)
{
  A _a = obj as A;
  if (_a != null && _a.m_i == this.m_i)
  {
   return true;
  }
  return base.Equals(obj);
}
public override int GetHashCode()
{
  return base.GetHashCode();
}
}

//测试
private void button1_Click(object sender, EventArgs e)
{
ArrayList al = new ArrayList();
al.Add(new A(1));
al.Add(new A(2));
al.Add(new A(3));

if (al.Contains(new A(2)))
{
MessageBox.Show("have");
}
else
{
MessageBox.Show("no");
}
}

public override bool Equals(object obj)
{
  A _a = obj as A;
  if (_a != null && _a.m_i == this.m_i)
  {
   return true;
  }
  return base.Equals(obj);
}
public override int GetHashCode()
{
  return base.GetHashCode();
}

这种方法是最标准的方法。
这两段代码是关键，其中GetHashcode不写也行，但会有编译警告。

override SenderAddress的Equals方法,否则它做的是对象地址的比较,即比较是否为同一对象,所以你的代码总是返回false