C＃CLR用户定义函数SqlBytes - InvalidOperationException

Question

我一直在编写一个从存储过程调用的sql clr udf，用于将未知文件类型（jpg，doc，pdf等）保存到文件系统中。 UFD接受一个SqlBytes类型的参数，它从调用存储过程（这是文件blob）传递varbinary（max）。问题是在CLR UDF的上下文中，我无法访问value属性甚至是SqlBytes文件参数的read方法，因为它返回了以下无效的异常错误。

我缩短了我的UDF以突出显示提到的问题。任何帮助将不胜感激。

先谢谢。

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错误

在此上下文中不允许数据访问。上下文是未标记为DataAccessKind.Read或SystemDataAccessKind.Read的函数或方法，是从表值函数的FillRow方法获取数据的回调，或者是UDT验证方法。

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堆栈跟踪

at System.Data.SqlServer.Internal.ClrLevelContext.CheckSqlAccessReturnCode(SqlAccessApiReturnCode eRc)
   at System.Data.SqlServer.Internal.ClrLevelContext.XvarProxyRead(CClrXvarProxy* pXvarProxy, UInt64 iPosition, Byte* pbBuffer, UInt32 cbCount)
   at System.Data.SqlServer.Internal.ClrLevelContext.System.Data.SqlServer.Internal.IXvarProxyAccessor.XvarProxyRead(CClrXvarProxy* , UInt64 , Byte* , UInt32 )
   at System.Data.SqlServer.Internal.StreamOnBlobHandle.Read(Byte* pbBuffer, UInt64 offset, UInt32 count)
   at System.Data.SqlServer.Internal.XvarBlobStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   at System.IO.BufferedStream.Read(Byte[] array, Int32 offset, Int32 count)
   at System.Data.SqlTypes.SqlBytes.Read(Int64 offset, Byte[] buffer, Int32 offsetInBuffer, Int32 count)
   at UserDefinedFunctions.SaveFileToFS(SqlBytes file, String fileName, String fileExtension, String path)

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CLR代码

using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using System.IO;
using System.Security.Permissions;
using System.Security.Principal;
using Microsoft.SqlServer.Server;

public partial class UserDefinedFunctions
{ 

    [Microsoft.SqlServer.Server.SqlFunction(DataAccess = DataAccessKind.Read, SystemDataAccess = SystemDataAccessKind.Read)]
    public static SqlString SaveFileToFS(SqlBytes file)
    {
        WindowsImpersonationContext newContext = null;
        WindowsIdentity newIdentity = SqlContext.WindowsIdentity;
        try
        {           
            if (newIdentity != null) newContext = newIdentity.Impersonate();

            byte[] buffer = new byte[8040 * 4];
            long offset = 0;
            long read = 0;

            //This file.Read will throw an error
            read = file.Read(offset, buffer, 0, buffer.Length);

            //this line will throw the same error
            buffer = (byte[])file.Value;

        catch (System.Exception ex1)
        {
            throw ex1;

        }
        finally
        {
            if (newContext != null) newContext.Undo();
        }
        return new SqlString("Success");
    }
};

---

所以只是为了完成这个线程 - 这里是CLR UDF的基本POC代码，它接受varbinary（max）文件blob，文件名，文件扩展名和写入路径，然后将其保存到定义的文件系统location（提供它具有适当的文件系统权限）。希望它可以帮助某人： - ）

using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using System.IO;
using System.Security.Permissions;
using System.Security.Principal;
using Microsoft.SqlServer.Server;

public partial class UserDefinedFunctions
{


    [Microsoft.SqlServer.Server.SqlFunction(DataAccess = DataAccessKind.Read , SystemDataAccess = SystemDataAccessKind.Read )]
    public static SqlString SaveFileToFS(SqlBytes file, string fileName, string fileExtension, string path)
    {

        WindowsImpersonationContext newContext = null;
        WindowsIdentity newIdentity = SqlContext.WindowsIdentity;
        try
        {

            long length = file.Length ;
            byte[] buffer = file.Value;
            long offset = 0;
            long read = 0;
            int times = 0;

            if (newIdentity != null) newContext = newIdentity.Impersonate();

            FileStream fs = new FileStream(path + fileName + fileExtension, System.IO.FileMode.Create, System.IO.FileAccess.Write);
            while (length > 1000)
            {
                fs.Write(buffer, 1000 * times, 1000);          

                length -= 1000;
                times++;
            }
            fs.Write(buffer, 1000 * times, (int)length);

            fs.Close();

        }
        catch (System.Exception ex1)
        {
            throw ex1;

        }
        finally
        {
            if (newContext != null) newContext.Undo();
        }
        return new SqlString(string.Format("Saved file: {0}{1} to path: {2}", fileName, fileExtension, path));
    }



};

Answer 1

我发现我在那里的模拟语句是从写入文件系统测试中遗留下来的。

如果我删除下面的代码行，那么所有代码​​都按预期工作。

WindowsImpersonationContext newContext = null;

WindowsIdentity newIdentity = SqlContext.WindowsIdentity;

和

if (newIdentity != null) newContext = newIdentity.Impersonate();