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小李菜刀:实现ICompare接口的通用对象比较类

2005-10-21 10:30 441 查看

using System;
using System.Collections ;
using System.Reflection ;
namespace ResTest
{
/// <summary>
/// 通用对象比较类，一般用于对一个对象数组按属性排序或查询
/// </summary>
public class ObjectCompare : System.Collections.IComparer
{
SortEntry[] _sortEntrys;
/**//// <summary>
/// 构造函数，制定排序方法
/// </summary>
/// <param name="type">对象的类型</param>
/// <param name="args">排序方法</param>
public ObjectCompare(Type type, params SortEntry[] args)
{
_sortEntrys = args;

//为防止因为指定的排序字段的值一样而造成每次的排序结果不同，再加属性和字段做为辅助
int j = args.Length;

PropertyInfo[] pis = type.GetProperties(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static | BindingFlags.Instance);
FieldInfo[] fis = type.GetFields(BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Static | BindingFlags.Instance);

_sortEntrys = new SortEntry[_sortEntrys.Length + pis.Length + fis.Length];

args.CopyTo(_sortEntrys, 0);

foreach (PropertyInfo pi in pis)
_sortEntrys[j++] = new SortEntry(pi.Name, pi.PropertyType, false);
foreach (FieldInfo fi in fis)
_sortEntrys[j++] = new SortEntry(fi.Name, fi.FieldType, false);
}

#region IComparer Members
int Compare(object x, object y, string propertyName, Type propertyType)
{
try
{
object sa = GetObjectPropertyValue(x, propertyName);
object sb = GetObjectPropertyValue(y, propertyName);
object ta = sa == DBNull.Value ? null : sa;
object tb = sb == DBNull.Value ? null : sb;
if (null == ta && null == tb)
return 0;
else if (null == ta && null != tb)
return -1;
else if (null != ta && null == tb)
return 1;
else
{
ta = Convert.ChangeType(sa, propertyType);
tb = Convert.ChangeType(sb, propertyType);
return ((IComparable)ta).CompareTo(tb);
}
}
catch
{
throw;
}
}
/// 比较两个对象的大小
/// </summary>
/// <param name="x"></param>
/// <param name="y"></param>
/// <returns>如果对象x大于对象y返回1，对象x小于对象y返回-1,相等则返回0</returns>
public int Compare(object x, object y)
{
try
{
int result;

for (int i = 0; i < _sortEntrys.Length; i++)
{
SortEntry se = _sortEntrys[i];
result = Compare(x, y, se.PropertyName, se.ProeprtyType);
if (se.Descend)
result = -result;
if (0 != result)
return result;
}
//为避免两个对象的属性值一样，再比较他们的hashcode
return x.GetHashCode().CompareTo(y.GetHashCode());
}
catch
{
throw;
}
}

#endregion
#region public object GetObjectPropertyValue(object obj, string propertyName)
/**//// <summary>
/// 得到对象的属性值
/// </summary>
/// <param name="obj">对象名</param>
/// <param name="propertyName">属性名</param>
/// <returns>属性的值，如不存在则反回Null</returns>
public object GetObjectPropertyValue(object instance, string propertyName)
{
try
{
Type t = instance.GetType();

return t.InvokeMember(propertyName,
BindingFlags.GetProperty | BindingFlags.GetField | BindingFlags.NonPublic | BindingFlags.Public | BindingFlags.Instance,
null, instance, null);
}
catch
{
throw new Exception(string.Format("未找到属性或字段{0}！", propertyName));
}
}
#endregion
}
/// <summary>
/// 排序方式设定方法非常好
/// </summary>
public struct SortEntry
{
/**//// <summary>
/// 构造函数
/// </summary>
/// <param name="propertyName">属性名</param>
/// <param name="value">是否倒序</param>
public SortEntry(string propertyName) : this(propertyName, typeof(string), false) { }

/**//// <summary>
/// 构造函数
/// </summary>
/// <param name="propertyName">属性名</param>
/// <param name="value">是否倒序</param>
public SortEntry(string propertyName, bool isDescend) : this(propertyName, typeof(string), isDescend) { }

/**//// <summary>
/// 构造函数
/// </summary>
/// <param name="propertyName">属性名</param>
/// <param name="value">是否倒序</param>
/// <param name="type">属性类型</param>
public SortEntry(string propertyName, Type type, bool isDescend)
{
if (propertyName + "" == "")
throw new Exception("属性名不能为空！");
if (type == null)
throw new Exception("属性的类型不能为空！");
_propertyName = propertyName;
_descend = isDescend;
_type = type;
}

/**//// <summary>
/// 属性名
/// </summary>
string _propertyName;
public string PropertyName { get { return _propertyName; } set { _propertyName = value; } }

/**//// <summary>
/// 是否倒序
/// </summary>
bool _descend;
public bool Descend { get { return _descend; } set { _descend = value; } }

Type _type;
//// <summary>
/// 属性的类型
/// </summary>
/// <value></value>
public Type ProeprtyType { get { return _type; } set { _type = value; } }
}
}

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