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Putting C# into SQL

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In my latest project we have come across a need to get results from a web service inside SQL Server. First basic reason why we wanted to have such an integration of web services is so that we could use them transparently in Microsoft Reporting Services. That of course is not the only reason we also wanted to use the same results as an input to some of our stored procedures and to do that we need to be able to get the results from the web service through a stored procedure or a table valued function.

The process it self is quite simple if you know where to begin. The beginning is in Sql servers implementation of CLR, with the use of CLR you can easily show those DBA’s how real programing is done :). Unfortunately for the DBA’s this is the only way this can be done so they need to trust us “developers” :). Seriously this is not such a problem to implement.

Pop open up Visual Studio and create a new “Sql Server Project” in the language of your preference (VB or C#) it’s all the same, but I will use C#. To start us off we need to configure the project first, so open “Project Properties” go to the “Build” section and find the option “Generate serialization assembly” set the option from auto to on. You have to do this because Sql server clr does not allow dynamic xml serialization, I guess it a security thing. Now when you build your project you will end up with two dlls one for you code “project.dll” and the other one for the serialized xml “project.serialization.dll”.

Now add your web service to the project just like in any other project trough the “Add web reference” menu, after you have done sou let’s add a new item to the project, add a stored procedure item to the project. Here is some sample code for the stored procedure.

[Microsoft.SqlServer.Server.SqlProcedure]
public static void WebServiceTest()
{
	// Initialize web service, adjust it for your service
	using (WebService ws = new WebService())
	{
		// Create a template record for the result set
		SqlDataRecord record = new SqlDataRecord(
			// The strings are the names of the columns of the result set
			// first field of type int
			metaData[0] = new SqlMetaData("field1", SqlDbType.Int),
			// second field of type varchar, equivalent of varchar(max)
			metaData[2] = new SqlMetaData("field2", SqlDbType.VarChar, -1),
			// third field of type decimal equivalent of decimal(12,4)
			metaData[4] = new SqlMetaData("field3", SqlDbType.Decimal, 12, 4));

		// Mark the begining of the result-set.
		SqlContext.Pipe.SendResultsStart(record);

		// Send rows back to the client.
		// Get the results from the web service, query a method on your web service
		foreach (Result item in ws.GetResult())
		{
			// set the value for field1
			record.SetInt32("field1", item.Value1);
			// set the value for field2
			record.SetString("field2", item.Value2);
			// set the value for field3
			record.SetDecimal("field3", item.Value3);

			// Send the row back to the client.
			SqlContext.Pipe.SendResultsRow(record);
		}

		// Mark the end of the result-set.
		SqlContext.Pipe.SendResultsEnd();
	}
}

Let’s look at this code. On line 4 is the initialization of the web service you will have to adjust it to your web service. Then you have to initialize a template record for your result set as is done on line 8 trough line 15. We initialize there columns of your result set column one is named “field1” and has a type of int, column two is named “field2” and has a type of varchar with length -1 or varchar(max), column three is named “field3” and has a type of decimal with length 12 and precision 4 or decimal(12,4). On line 18 we start the return of our result set and tell sql that we will be returning items based on record template we have just created. On lines 22 through 33 we iterate through our result set, set the values and use the Sql pipe to send the results. On line 36 we end the sending of results. That is it for the code part, so now we need to register the assembly in the sql server.First you have to set the database trustworthy option to on.

ALTER DATABASE DatabaseName SET TRUSTWORTHY ON

If we do not set this option to on we can’t register our assemblies as UNSAFE, and if we cant do that Sql clr wont allow us to connect to the web service. I think that you could use the EXTERNAL_ACCESS option but I have not tried that.

CREATE ASSEMBLY [AssemblyName]
FROM'C:\AssemblyPath\AssemblyName.dll'
WITH PERMISSION_SET = UNSAFE
GO
CREATE ASSEMBLY [AssembyName]
FROM'C:\AssemblyPath\AssemblyName.Serialization.dll'
WITH PERMISSION_SET = UNSAFE
GO
CREATE PROCEDURE [SchemaName].[WebServiceTest]
AS
EXTERNAL NAME [AssemblyName].Namespace.WebServiceTest

That is it now you can test out your new sql clr procedure.

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Written by Luka Ferlež

March 22, 2008 at 23:39

Posted in C#, Programing, SQL

Tagged with , ,

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