一般情况下我只需要使用ArrayList.Contains（）方法就可以判断某个元素是否存在，但如果ArrayList中的为自定义的类就需要自己实现，如下面例子：

如我们有一个类：

public class Employee{     public int EmployeeID     {            get;set;     }     public string EmployeeName     {           get;set;     }     public DateTime BirthDate     {           get; set;     }

}

我们要实现对ArrayList中存储的Employee 进行查找。先定义两个枚举：

public enum MemType{    IntegerType = 1, StringType = 2, DateTimeType = 3, BooleanType = 4};public enum CmpOperator{    GreaterThan = 1, LessThan = 2, EqualTo = 3}

下面是具体实现：

public static int Search(ArrayList objArr, string valueToSearch, string FieldName, MemType memType, CmpOperator comOp){    if (memType == MemType.StringType || memType == MemType.BooleanType)    {        comOp = CmpOperator.EqualTo;    }    for (int i = 0; i < objArr.Count; i++)    {        Type t = objArr[0].GetType();        System.Reflection.FieldInfo[] arrInner = t.GetFields();        System.Reflection.PropertyInfo PI = t.GetProperty(FieldName);        string str = PI.GetValue(objArr[i], null).ToString();        switch (memType)        {            case MemType.BooleanType:                if (Convert.ToBoolean(str) == Convert.ToBoolean(valueToSearch))                {                    return i;                }                break;            case MemType.DateTimeType:                switch (comOp)                {                    case CmpOperator.EqualTo:                        if (Convert.ToDateTime(str).CompareTo(Convert.ToDateTime(valueToSearch)) == 0)                        {                            return i;                        }                        break;                    case CmpOperator.GreaterThan:                        if (Convert.ToDateTime(str).CompareTo(Convert.ToDateTime(valueToSearch)) > 0)                        {                            return i;                        }                        break;                    case CmpOperator.LessThan:                        if (Convert.ToDateTime(str).CompareTo(Convert.ToDateTime(valueToSearch)) < 0)                        {                            return i;                        }                        break;                }                break;            case MemType.IntegerType:                switch (comOp)                {                    case CmpOperator.EqualTo:                        if (Convert.ToInt32(str) == Convert.ToInt32(valueToSearch))                        {                            return i;                        }                        break;                    case CmpOperator.GreaterThan:                        if (Convert.ToInt32(str) > Convert.ToInt32(valueToSearch))                        {                            return i;                        }                        break;                    case CmpOperator.LessThan:                        if (Convert.ToInt32(str) < Convert.ToInt32(valueToSearch))                        {                            return i;                        }                        break;                }                break;            case MemType.StringType:                if (str.Contains(valueToSearch))                {                    return i;                }                break;        }    }    return -1;}

测试代码如下：

static void Main(string[] args) {     ArrayList al = new ArrayList();     Employee emp1 = new Employee();     emp1.EmployeeID = 2;     emp1.EmployeeName = "cary";                emp1.BirthDate = new DateTime(1982, 4, 1);     Employee emp2 = new Employee();     emp2.EmployeeID = 3;     emp2.EmployeeName = "james";                emp2.BirthDate = new DateTime(1983, 4, 1);     al.Add(emp1);     al.Add(emp2);     int searIndex = Search(al, "3", "EmployeeID", MemType.IntegerType, CmpOperator.EqualTo);     Console.WriteLine(searIndex);     Console.ReadLine();         }

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