使用c#构造date数据类型

using System; 
using System.Data; 
using System.Data.SqlClient; 
using System.Data.SqlTypes; 
using Microsoft.SqlServer.Server; 
[Serializable] 
[Microsoft.SqlServer.Server.SqlUserDefinedTypeFormat.UserDefined ,IsByteOrdered=true,MaxByteSize =20,ValidationMethodName="ValidateDate")] 
public struct date : INullable,IBinarySerialize 
{ 
// 私有成员 
private bool m_Null; 
private string m_date; 
public override string ToString() 
{ 
if (this.m_Null) 
return "null"; 
else 
{ 
return this.m_date; 
} 
} 
public bool IsNull 
{ 
get 
{ 
return m_Null; 
} 
} 
public static date Null 
{ 
get 
{ 
date h = new date(); 
h.m_Null = true; 
return h; 
} 
} 
public static date Parse(SqlString s) 
{ 
if (s.IsNull || (!s.IsNull && s.Value.Equals(""))) 
return Null; 
else 
{ 
date u = new date(); 
string[] xy = s.Value.Split(" ".ToCharArray()); 
u.m_date = xy[0]; 
if (!u.ValidateDate()) 
throw new ArgumentException ("无效的时间"); 
return u; 
} 
} 
public string _date 
{ 
get 
{ 
return this.m_date; 
} 
set 
{ 
m_Null = true; 
m_date = value; 
if (!ValidateDate()) 
throw new ArgumentException("无效的时间"); 
} 
} 
public void Write(System.IO.BinaryWriter w) 
{ 
byte header = (byte)(this.IsNull ? 1 : 0); 
w.Write(header); 
if (header == 1) 
{ 
return; 
} 
w.Write(this.m_date); 
} 
public void Read(System.IO.BinaryReader r) 
{ 
byte header = r.ReadByte(); 
if (header == 1) 
{ 
this.m_Null = true; 
return; 
} 
this.m_Null = false ; 
this.m_date = r.ReadString(); 
} 
private bool ValidateDate() //判断时间是否有效 
{ 
try 
{ 
DateTime dt = Convert.ToDateTime(m_date); 
return true; 
} 
catch 
{ 
return false; 
} 
} 
} 
 
5、按F5进行部署 
6、测试： 
 代码如下:

CREATE TABLE tb(id int,dt dbo.Date DEFAULT CONVERT(dbo.Date,CONVERT(VARCHAR(10),GETDATE(),120))); 
insert into tb(id) values(1) 
SELECT id,dt=dt.ToString() FROM tb; 
/* 
结果： 
id dt 
1 2009-08-14 
*/ 
DROP TABLE tb; 
 
注： 
1、 如果要对date类型进行日期的加减，可以调用ToString()方法