Question

I need to call an external DLL that resides in the PC that hosts the SQL Server from various clients in order to get digital signatures.

I thought using SQLCLR is a good idea.I have issues though…

I wrote this in order to call the external dll function inside the C# dll

[Microsoft.SqlServer.Server.SqlProcedure]
public static void Sign( SqlString receipt, out SqlString signature)
{
    short result=0;
    string arg = "";
    string commPort = "1";
    signature = "";

    bool btrue = true, bfalse = false;

    string CommPort = commPort.ToString();
    string Receipt = receipt.ToString();
    string Signature = signature.ToString();

    ExtDll.Box ExtBox = new Box();
    ExtBox.Sign_(ref CommPort,Receipt,ref result,ref Signature,ref bfalse,ref arg,ref btrue);

    signature = (SqlString)Signature;
}

I wrote the asembly for the SQL Server

CREATE ASSEMBLY Mybox 
FROM 'C:\Users\Panos\Documents\Visual Studio 2010\Projects\DigitalSignature\Extbox\bin\Debug\Extbox.dll'   
WITH PERMISSION_SET = UNSAFE  

I wrote a stored procedure

CREATE PROC sp_extbox (@receipt char(2048), @signature char(100) out)
AS
EXTERNAL NAME Mybox.Signatures.Sign 

But when I execute the above script I get

CREATE PROCEDURE for “sp_extbox” failed because T-SQL and CLR types for parameter “@receipt” do not match.

Answer 1

I believe an SqlString corresponds to nvarchar.

So, try this instead of your current last script:

CREATE PROC sp_extbox (@receipt nvarchar(4000), @signature nvarchar(4000) out)
AS
EXTERNAL NAME Mybox.Signatures.Sign