平时做技术实践时，很多问题不是概念不会，而是细节没串起来。拿“SQL2005CLR函数扩展-解析天气服务的实现方法”来说，它看着像小点，放到项目里常会牵出环境、配置、兼容性和维护成本。下面按实际采用顺序，把思路、关键写法和容易踩坑的地方讲清楚，便于大家直接对照操作。

复制代码 代码如下所示:

using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using System.Collections;
using System.Collections.Generic;
using Microsoft.SqlServer.Server;

public partial class UserDefinedFunctions
{

[SqlFunction (TableDefinition = "city nvarchar(100),date nvarchar(100),general nvarchar(100),temperature nvarchar(100),wind nvarchar(100)" , Name = "GetWeather" , FillRowMethodName = "FillRow" )]
public static IEnumerable GetWeather()
{
System.Collections.Generic.List <Item > list = GetData();
return list;
}
public static void FillRow(Object obj, out SqlString city, out SqlString date, out SqlString general, out SqlString temperature, out SqlString wind)
{
Item data = (Item )obj;
city = data.city;
date = data.date;
general = data.general;
temperature = data.temperature;
wind = data.wind;
}

class Item
{
public string city;
public string date;
public string general;
public string temperature;
public string wind;
}
static System.Collections.Generic.List <Item > GetData()
{
System.Collections.Generic.List <Item > ret = new List <Item >();
//try
//{

string url = "（链接已移除）" ;
System.Net.WebClient wb = new System.Net.WebClient ();
byte [] b = wb.DownloadData(url);
string data = System.Text.Encoding .Default.GetString(b);
System.Xml.XmlDocument doc = new System.Xml.XmlDocument ();
doc.LoadXml(data);

foreach (System.Xml.XmlNode node in doc.ChildNodes[1])
{
string city = GetXMLAttrib(node, "name" );
foreach (System.Xml.XmlNode subnode in node.ChildNodes)
{
Item item = new Item ();
item.city = city;
item.date = GetXMLAttrib(subnode, "date" );
item.general = GetXMLAttrib(subnode, "general" );
item.temperature = GetXMLAttrib(subnode, "temperature" );
item.wind = GetXMLAttrib(subnode, "wind" );
ret.Add(item);
}
}

//}
//catch(Exception ex)
//{
// SqlContext.Pipe.Send(ex.Message);
//}
return ret;
}

static string GetXMLAttrib(System.Xml.XmlNode node, string attrib)
{
try
{
return node.Attributes[attrib].Value;
}
catch
{
return string .Empty;
}
}
};

复制代码 代码如下所示:

drop function dbo. xfn_GetWeather
drop ASSEMBLY TestWeather
go
CREATE ASSEMBLY TestWeather FROM 'd:/sqlclr/TestWeather.dll' WITH PERMISSION_SET = UnSAFE;
--
go
CREATE FUNCTION dbo. xfn_GetWeather ()
RETURNS table ( city nvarchar ( 100), date nvarchar ( 100), general nvarchar ( 100), temperature nvarchar ( 100), wind nvarchar ( 100))
AS EXTERNAL NAME TestWeather. UserDefinedFunctions. GetWeather