这个方法比较简单，用Microsoft.VisualBasic命名空间下强大的字符串处理函数就可以了
c#代码如下，编译为BigConvertor.dll
--------------------------------------------------------------------------------
代码如下：

using System;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;

public partial class UserDefinedFunctions
{
    [Microsoft.SqlServer.Server.SqlFunction ]
    public static SqlString BigToGB(SqlString inString)
    {
        if (inString.IsNull) return SqlString .Null;
        return (Microsoft.VisualBasic.Strings .StrConv(inString.Value, Microsoft.VisualBasic.VbStrConv .SimplifiedChinese, 0));
    }
     [Microsoft.SqlServer.Server.SqlFunction ]
    public static SqlString GBToBig(SqlString inString)
    {
        if (inString.IsNull) return SqlString .Null;
        return (Microsoft.VisualBasic.Strings .StrConv(inString.Value, Microsoft.VisualBasic.VbStrConv .TraditionalChinese, 0));
    }
};

--------------------------------------------------------------------------------
部署代码如下
--------------------------------------------------------------------------------
代码如下：

CREATE ASSEMBLY BigConvertor FROM 'E:/sqlclrdata/BigConvertor.dll' WITH PERMISSION_SET = UnSAFE;
--
go
CREATE FUNCTION dbo. xfn_BigToGB 
(  
    @value nvarchar ( max )
)    
RETURNS nvarchar ( max )
AS EXTERNAL NAME BigConvertor. UserDefinedFunctions. BigToGB
go
CREATE FUNCTION dbo. xfn_GBToBig 
(  
    @value nvarchar ( max )
)    
RETURNS nvarchar ( max )
AS EXTERNAL NAME BigConvertor. UserDefinedFunctions. GBToBig

go

--------------------------------------------------------------------------------
测试代码如下
--------------------------------------------------------------------------------
/* 测试 */
select dbo. xfn_GBToBig( ' 简体与繁体文的转换 ' )
-- 繁文的
select dbo. xfn_BigToGB( ' 繁文的 ' )
-- 简体与繁体文的转换