简单例子
首先写一段简单的 C# 代码，然后把它编译成 dll。
namespace Bussiness
{
public class UserFunctions
{
public static string UserLogin(string username, string password)
{
var random = new Random();
var isSuccess = random.Next() % 2 == 0;
return isSuccess ? "登录成功" : "登录失败";
}
}
}接下来需要做的就是数据库参数配置，开启 CLR 支持，并且指定某个数据库支持 unsafe 模式。
EXEC sp_configure 'clr enabled', 1;
RECONFIGURE;
GO
ALTER DATABASE MyTestDB SET TRUSTWORTHY ON;
GO 为了能够调到 C# 的 UserLogin 方法，需要 SQLSERVER 先导入这个程序集，然后再以 Function 映射其中方法即可
CREATE ASSEMBLY clr_Bussiness
FROM 'D:\Bussiness.dll'
WITH PERMISSION_SET = UNSAFE;
GO
CREATE FUNCTION dbo.clr_UserLogin
(
@username AS NVARCHAR(100),
@password AS NVARCHAR(100)
)
RETURNS NVARCHAR(100)
AS
EXTERNAL NAME clr_Bussiness.[Bussiness.UserFunctions].UserLogin;
GO 创建完了之后，可以观察 assembly 开头的几个系统视图。
SELECT * FROM sys.assemblies
SELECT * FROM sys.assembly_files;
SELECT * FROM sys.assembly_modules;接下来调用一下刚才创建的 clr_UserLogin 函数。
SELECT dbo.clr_UserLogin(N'jack',N'123456') AS 'State'
GO 10
从图中看登录结果是随机的，说明 C# 的 Random 函数起到了作用。
WinDbg 观察
从案例的运行结果看，推测在 SQLSERVER 中应该承载了一个 CLR 运行环境，那是不是这样呢？可以用 WinDbg 附加到 sqlservr.exe 进程，用 lm观察下模块加载情况。
0:092> lm
start end module name
...
00007ff8`d3960000 00007ff8`d3aaf000 clrjit (deferred)
00007ff8`de040000 00007ff8`deb02000 clr (deferred)
...
0:092> !eeversion
4.8.4300.0 free
Server mode with 12 gc heaps
SOS Version: 4.8.4300.0 retail build从输出看果然加载了 clr 和 clrjit 动态链接库，当前还是 gc server 模式。
接下来再验证一个问题，既然 clr_UserLogin 函数会显示 登录成功/登录失败，那必然会调用 C# 的 UserLogin 方法，可以在 WinDbg 中对 UserLogin 方法下一个断点观察一下这个调用过程
0:090> !name2ee Bussiness!Bussiness.UserFunctions.UserLogin
Module: 00007ff87ee37988
Assembly: Bussiness, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null
Token: 0000000006000001
MethodDesc: 00007ff87ee38020
Name: Bussiness.UserFunctions.UserLogin(System.String, System.String)
JITTED Code Address: 00007ff87ec560d0
0:090> bp 00007ff87ec560d0
0:090> g从输出信息看 UserLogin 方法已经被 JIT 过了，用 bp 下完断点之后，继续 g，然后在 SSMS 上再次执行查询就可以成功命中啦。
0:090> k
# Child-SP RetAddr Call Site
00 000000df`1557ae48 00007ff8`7ee500b6 0x00007ff8`7ec560d0
01 000000df`1557ae50 00007ff8`7ec55ef1 0x00007ff8`7ee500b6
02 000000df`1557aeb0 00007ff8`de04222e 0x00007ff8`7ec55ef1
03 000000df`1557af00 00007ff8`a2b79ff3 clr!UMThunkStub+0x6e
04 000000df`1557af90 00007ff8`a2b741bd sqllang!CallProtectorImpl::CallWithSEH<AppDomainCallTraits,void,FunctionCallBinder_3<void,void (__cdecl*)(void (__cdecl*)(void * __ptr64),void * __ptr64,enum ESqlReturnCode * __ptr64),void (__cdecl*)(void * __ptr64),void * __ptr64,enum ESqlReturnCode * __ptr64> const >+0x23
05 000000df`1557afc0 00007ff8`a2b6bfc4 sqllang!CallProtectorImpl::CallExternalFull<AppDomainUserCallTraits,void,FunctionCallBinder_3<void,void (__cdecl*)(CXVariant * __ptr64,CXVariant * __ptr64,CClrLobContext * __ptr64),CXVariant * __ptr64,CXVariant * __ptr64,CClrLobContext * __ptr64> const >+0x2dd
06 000000df`1557b130 00007ff8`a2bda602 sqllang!CAppDomain::InvokeClrFn+0xd4
07 000000df`1557b1d0 00007ff8`aef51ee7 sqllang!UDFInvokeExternalImpl+0xb72
08 000000df`1557b7e0 00007ff8`9de52e24 sqlTsEs!CEsExec::GeneralEval4+0xe7
09 000000df`1557b8b0 00007ff8`9de52d64 sqlmin!CQScanProjectNew::EvalExprs+0x18f
0a 000000df`1557b920 00007ff8`9ddd8759 sqlmin!CQScanProjectNew::GetRow+0x98
0b 000000df`1557b970 00007ff8`9ddc73de sqlmin!CQScanLightProfileNew::GetRow+0x19
0c 000000df`1557b9a0 00007ff8`a25e51d7 sqlmin!CQueryScan::GetRow+0x80
0d 000000df`1557b9d0 00007ff8`a32a78b2 sqllang!CXStmtQuery::ErsqExecuteQuery+0x3d8
0e 000000df`1557bb40 00007ff8`a2bc2451 sqllang!CXStmtSelect::XretDoExecute+0x342
0f 000000df`1557bc10 00007ff8`a2b733d3 sqllang!UM_LoopbackForStatementExecution+0x191
10 000000df`1557bd00 00007ff8`de48e940 sqllang!AppDomainCallback<FunctionCallBinder_5<void,void (__cdecl*)(CXStmtQuery * __ptr64,CCompExecCtxtStmt const * __ptr64,CMsqlExecContext * __ptr64,unsigned long * __ptr64,enum ESqlReturnCode * __ptr64),CXStmtQuery * __ptr64,CCompExecCtxtStmt const * __ptr64,CMsqlExecContext * __ptr64,unsigned long * __ptr64,enum ESqlReturnCode * __ptr64> >+0x23
11 000000df`1557bd40 00007ff8`de48e193 clr!ExecuteInAppDomainHelper+0x40
12 000000df`1557bd80 00007ff8`a2b79f39 clr!CorHost2::ExecuteInAppDomain+0x3a0
13 000000df`1557c0a0 00007ff8`a2b73a86 sqllang!CallProtectorImpl::CallWithSEH<AppDomainCallTraits,long,MethodCallBinder_3<long,ICLRRuntimeHost,long (__cdecl ICLRRuntimeHost::*)(unsigned long,long (__cdecl*)(void * __ptr64),void * __ptr64) __ptr64,unsigned long,long (__cdecl*)(void * __ptr64),void * __ptr64> >+0x29
14 000000df`1557c0d0 00007ff8`a2b6c2d0 sqllang!CallProtectorImpl::CallExternalFull<AppDomainCallTraits,long,MethodCallBinder_3<long,ICLRRuntimeHost,long (__cdecl ICLRRuntimeHost::*)(unsigned long,long (__cdecl*)(void * __ptr64),void * __ptr64) __ptr64,unsigned long,long (__cdecl*)(void * __ptr64),void * __ptr64> >+0x186
15 000000df`1557c170 00007ff8`a32a72f4 sqllang!CAppDomain::LoopbackForStatementExecution+0x180
16 000000df`1557c230 00007ff8`a32a79ad sqllang!CXStmtQuery::XretCLRExecute+0x104
17 000000df`1557c2a0 00007ff8`a25e4a65 sqllang!CXStmtSelect::XretExecute+0x4a
18 000000df`1557c370 00007ff8`a25e44a8 sqllang!CMsqlExecContext::ExecuteStmts<1,1>+0x8f2
19 000000df`1557cf10 00007ff8`a25e3a2c sqllang!CMsqlExecContext::FExecute+0x936
1a 000000df`1557def0 00007ff8`a25ee67b sqllang!CSQLSource::Execute+0xc5c
1b 000000df`1557e3d0 00007ff8`a25ed815 sqllang!process_request+0xca6
1c 000000df`1557ead0 00007ff8`a25ed5ef sqllang!process_commands_internal+0x4b7
1d 000000df`1557ec00 00007ff8`b1e46523 sqllang!process_messages+0x1d6
1e 000000df`1557ede0 00007ff8`b1e46e6d sqldk!SOS_Task::Param::Execute+0x232
1f 000000df`1557f3e0 00007ff8`b1e46c75 sqldk!SOS_Scheduler::RunTask+0xa5
20 000000df`1557f450 00007ff8`b1e6b160 sqldk!SOS_Scheduler::ProcessTasks+0x39d
21 000000df`1557f570 00007ff8`b1e6aa5b sqldk!SchedulerManager::WorkerEntryPoint+0x2a1
22 000000df`1557f640 00007ff8`b1e6afa4 sqldk!SystemThreadDispatcher::ProcessWorker+0x3ed
23 000000df`1557f940 00007ff8`f6d86fd4 sqldk!SchedulerManager::ThreadEntryPoint+0x3b5
24 000000df`1557fa30 00007ff8`f865cec1 KERNEL32!BaseThreadInitThunk+0x14
25 000000df`1557fa60 00000000`00000000 ntdll!RtlUserThreadStart+0x21request 请求，然后达到了托管方法 UserLogin，顶部的三行线程栈可以用 !clrstack
0:090> !clrstack
OS Thread Id: 0x6df4 (90)
Child SP IP Call Site
000000df1557ae48 00007ff87ec560d0 AQMN.Bussiness.UserFunctions.UserLogin(System.String, System.String)
000000df1557ae50 00007ff87ee500b6 DynamicClass.SQLCLR_Eval(IntPtr, IntPtr, IntPtr)
000000df1557aeb0 00007ff87ec55ef1 DomainBoundILStubClass.IL_STUB_ReversePInvoke(Int64, Int64, Int64)
000000df1557bf18 00007ff8de04222e [ContextTransitionFrame: 000000df1557bf18]
看来SQLSERVER 内嵌了 CLR，让 sqlservr 进程成了一种托管和非托管的混合环境，托管的 C#，VB，F# 可以助 SQLSERVER 更加强大。
