In-Process Data Access Sample

Article
04/01/2012

The InProcessDataAccess sample contains a number of simple functions that demonstrate various features of the SQL Server CLR in-process data access provider.

Prerequisites

To create and run this project the following the following software must be installed:

SQL Server or SQL Server Express. You can obtain SQL Server Express free of charge from the SQL Server Express Documentation and Samples Web site
The AdventureWorks database that is available at the SQL Server Developer Web site
.NET Framework SDK 2.0 or later or Microsoft Visual Studio 2005 or later. You can obtain .NET Framework SDK free of charge.
In addition, the following conditions must be met:
The SQL Server instance you are using must have CLR integration enabled.
In order to enable CLR integration, perform the following steps:

Enabling CLR Integration
- Execute the following Transact-SQL commands:
sp_configure 'clr enabled', 1

GO

RECONFIGURE

GO

Note

To enable CLR, you must have ALTER SETTINGS server level permission, which is implicitly held by members of the sysadmin and serveradmin fixed server roles.
The AdventureWorks database must be installed on the SQL Server instance you are using.
If you are not an administrator for the SQL Server instance you are using, you must have an administrator grant you CreateAssembly permission to complete the installation.

Building the Sample

Create and run the sample by using the following instructions:

Open a Visual Studio or .NET Framework command prompt.
If necessary, create a directory for your sample. For this example, we will use C:\MySample.
In c:\MySample, create inprocda.vb (for the Visual Basic sample) or inprocda.cs (for the C# sample) and copy the appropriate Visual Basic or C# sample code (below) into the file.
Compile the sample code into the required assembly from the command line prompt by executing one of the following, depending on your choice of language.
- Vbc /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Data.dll,C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.dll,C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Xml.dll /target:library InProcDA.vb
- Csc /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Data.dll /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.dll /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.XML.dll /target:library inprocda.cs
Copy the Transact-SQL installation code into a file and save it as Install.sql in the sample directory.
If the sample is installed in a directory other then C:\MySample\, edit the file Install.sql as indicated to point to that location.
Deploy the assembly, stored procedure and functions by executing
- sqlcmd -E -I -i install.sql
Copy the Transact-SQL installation code into a file and save it as test.sql in the sample directory.
Test the application by executing the following line at the command prompt:
- sqlcmd -E -I -i test.sql
Copy the Transact-SQL cleanup script into a file and save it as cleanup.sql in the sample directory.
Execute the script with the following command
- sqlcmd -E -I -i cleanup.sql

Sample Code

The following are the code listings for this sample.

using System;
using System.Data;
using System.Data.Sql;
using System.Data.SqlTypes;
using System.Data.SqlClient;
using Microsoft.SqlServer.Server;
public sealed class DataAccessDemo
{
        private DataAccessDemo()
        {
        }

        /// <summary>
/// Simple example to send a message to the client.
/// </summary>
public static void SendMessage(string msg)
{
SqlContext.Pipe.Send("Message from server: " + msg);
}

/// <summary>
/// Simple example of performing data access within
/// a function
/// </summary>
/// <returns></returns>
        [Microsoft.SqlServer.Server.SqlFunction(DataAccess = Microsoft.SqlServer.Server.DataAccessKind.Read)]
public static string ReportSqlVersion()
{
            using (SqlConnection conn = new SqlConnection("context connection=true"))
            {
                //create a command from the current context
                SqlCommand cmd = conn.CreateCommand();

                //execute something
                cmd.CommandText = "select @@version";

                conn.Open();
                //return results as scalar
                return (string)cmd.ExecuteScalar();
            }
}


/// <summary>
/// Create a result set on the fly and send it to the client.
/// </summary>
public static void SendTransientResultSet()
{
//create the metadata for the columns
            Microsoft.SqlServer.Server.SqlMetaData[] columnSchema 
                = new Microsoft.SqlServer.Server.SqlMetaData[] {
new Microsoft.SqlServer.Server.SqlMetaData("stringcol", SqlDbType.NVarChar, 128)
};

//create a record based on that metadata
            SqlDataRecord newRecord = new SqlDataRecord(columnSchema);

//populate it
newRecord.SetString(0, "Hello World!");

//send it
SqlContext.Pipe.Send(newRecord);
}

/// <summary>
/// Execute a command and send the results to the client directly.
/// </summary>
public static void ExecuteToClient()
{
            using (SqlConnection conn = new SqlConnection("context connection=true"))
            {
                SqlCommand cmd = conn.CreateCommand();

                cmd.CommandText = "select @@version";
                conn.Open();
                SqlContext.Pipe.ExecuteAndSend(cmd);
            }
}

/// <summary>
/// Execute a command and send the resultig reader to the client
/// </summary>
public static void SendReaderToClient()
{
            using (SqlConnection conn = new SqlConnection("context connection=true"))
            {
                SqlCommand cmd = conn.CreateCommand();

                cmd.CommandText = "select @@version";
                conn.Open();
                SqlDataReader rdr = cmd.ExecuteReader();
                try
                {
                    SqlContext.Pipe.Send(rdr);
                }
                finally
                {
                    rdr.Close();
                }
            }
}

};

Visual Basic

Imports Microsoft.SqlServer.Server
Imports Microsoft.VisualBasic
Imports System
Imports System.Collections
Imports System.Data
Imports System.Data.Sql
Imports System.Data.SqlClient
Imports System.Data.SqlTypes
Imports System.Diagnostics
Partial Public NotInheritable Class DataAccessDemo
    Private Sub New()
    End Sub

    ''' <summary>
    ''' Simple example of performing data access within a function
    ''' </summary>
    ''' <returns></returns>
    <SqlFunction(DataAccess:=DataAccessKind.Read)> _
    Public Shared Function ReportSqlVersion() As SqlString
        Using conn As New SqlConnection("context connection=true")
            'create a command from the current context
            Dim cmd As SqlCommand = conn.CreateCommand()

            'execute something
            cmd.CommandText = "SELECT @@VERSION"

            conn.Open()

            'return results as scalar
            Return CType(cmd.ExecuteScalar(), String)
        End Using
    End Function

    ''' <summary>
    ''' Simple example to send a message to the client.
    ''' </summary>
    Public Shared Sub SendMessage(ByVal msg As String)
        SqlContext.Pipe.Send(("Message from server: " & msg))
    End Sub

    ''' <summary>
    ''' Create a result set on the fly and send it to the client.
    ''' </summary>
    Public Shared Sub SendTransientResultSet()
        'create the metadata for the columns
        Dim columnSchema() As Microsoft.SqlServer.Server.SqlMetaData _
            = {New SqlMetaData("stringcol", SqlDbType.NVarChar, 128)}

        'create a record based on that metadata
        Dim newRecord As New SqlDataRecord(columnSchema)

        'populate it
        newRecord.SetString(0, "Hello World!")

        'send it
        SqlContext.Pipe.Send(newRecord)
    End Sub

    ''' <summary>
    ''' Execute a command and send the results to the client directly.
    ''' </summary>
    Public Shared Sub ExecuteToClient()
        Using conn As New SqlConnection("context connection=true")
            Dim cmd As SqlCommand = conn.CreateCommand()

            cmd.CommandText = "SELECT @@VERSION"
            conn.Open()
            SqlContext.Pipe.ExecuteAndSend(cmd)
        End Using
    End Sub

    ''' <summary>
    ''' Execute a command and send the resulting reader to the client
    ''' </summary>
    Public Shared Sub SendReaderToClient()
        Using conn As New SqlConnection("context connection=true")
            Dim cmd As SqlCommand = conn.CreateCommand()
            cmd.CommandText = "SELECT @@VERSION"
            conn.Open()
            Dim rdr As SqlDataReader = cmd.ExecuteReader()
            Try
                SqlContext.Pipe.Send(rdr)
            Finally
                rdr.Close()
            End Try
        End Using
    End Sub

End Class

This is the Transact-SQL installation script (Install.sql), which deploys the assembly and creates the stored procedures and function required by this example.

USE AdventureWorks;
GO
IF EXISTS (SELECT * FROM sys.procedures WHERE name = N'SendMessage')
DROP PROCEDURE SendMessage;
GO

IF EXISTS (SELECT * FROM sys.procedures WHERE name = N'SendTransientResultSet')
DROP PROCEDURE SendTransientResultSet;
GO

IF EXISTS (SELECT * FROM sys.procedures WHERE name = N'ExecuteToClient')
DROP PROCEDURE ExecuteToClient;
GO

IF EXISTS (SELECT * FROM sys.procedures WHERE name = N'SendReaderToClient')
DROP PROCEDURE SendReaderToClient;
GO

IF EXISTS (SELECT * FROM sys.objects WHERE name = N'ReportSqlVersion' and (type = 'FS' or type = 'FT'))  
DROP FUNCTION [ReportSqlVersion];
GO

IF EXISTS (SELECT * FROM sys.assemblies WHERE name = N'InProcDA') DROP ASSEMBLY InProcDA;
GO
DECLARE @SamplesPath nvarchar(1024)

-- You may need to modify the value of the this variable if you have installed the sample someplace other than the default location.
set @SamplesPath = N'C:\MySample\'
CREATE ASSEMBLY InProcDA FROM @SamplesPath + 'InProcDA.dll'
WITH permission_set = SAFE;
GO

CREATE PROCEDURE [SendMessage] @msg nvarchar(4000)
AS
EXTERNAL NAME [InProcDA].[DataAccessDemo].[SendMessage];
GO

CREATE FUNCTION [ReportSqlVersion]() RETURNS nvarchar(4000)
AS EXTERNAL NAME [InProcDA].[DataAccessDemo].[ReportSqlVersion];
GO

CREATE PROCEDURE [SendTransientResultSet]
AS
EXTERNAL NAME [InProcDA].[DataAccessDemo].[SendTransientResultSet];
GO

CREATE PROCEDURE [ExecuteToClient]
AS
EXTERNAL NAME [InProcDA].[DataAccessDemo].[ExecuteToClient];
GO

CREATE PROCEDURE [SendReaderToClient]
AS
EXTERNAL NAME [InProcDA].[DataAccessDemo].[SendReaderToClient];
GO

The following Transact-SQL (test.sql) tests the example by exercising the stored procedures and function defined in this sample.

USE AdventureWorks;
GO

-- send a message to the client
EXEC SendMessage  N'This is a test message.';

-- exec a function that does data access
SELECT dbo.ReportSqlVersion();

-- exec the proc that sends a result set to the client
EXEC SendTransientResultSet;

EXEC ExecuteToClient;

EXEC SendReaderToClient;

USE master;
GO

The following Transact-SQL removes the assembly, function and stored procedures from the database.

USE AdventureWorks
GO

IF EXISTS (SELECT * FROM sys.procedures WHERE name = N'SendMessage')
DROP PROCEDURE SendMessage;
GO

IF EXISTS (SELECT * FROM sys.procedures WHERE name = N'SendTransientResultSet')
DROP PROCEDURE SendTransientResultSet;
GO

IF EXISTS (SELECT * FROM sys.procedures WHERE name = N'ExecuteToClient')
DROP PROCEDURE ExecuteToClient;
GO

IF EXISTS (SELECT * FROM sys.procedures WHERE name = N'SendReaderToClient')
DROP PROCEDURE SendReaderToClient;
GO

IF EXISTS (SELECT * FROM sys.objects WHERE name = N'ReportSqlVersion' and (type = 'FS' or type = 'FT'))  
DROP FUNCTION [ReportSqlVersion];
GO

IF EXISTS (SELECT * FROM sys.assemblies WHERE name = N'InProcDA') DROP ASSEMBLY InProcDA;
GO

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In-Process Data Access Sample

Prerequisites

Enabling CLR Integration

Building the Sample

Create and run the sample by using the following instructions:

Sample Code

See Also

Concepts

Additional resources