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Loading the Output of a Local Package

Client applications can read the output of Integration Services packages when the output is saved to SQL Server destinations by using ADO.NET, or when the output is saved to a flat file destination by using the classes in the System.IO namespace. However, a client application can also read the output of a package directly from memory, without the need for an intermediate step to persist the data. The key to this solution is the Microsoft.SqlServer.Dts.DtsClient namespace, which contains specialized implementations of the IDbConnection, IDbCommand, and IDbDataParameter interfaces from the System.Data namespace. The assembly Microsoft.SqlServer.Dts.DtsClient.dll is installed by default in %ProgramFiles%\Microsoft SQL Server\100\DTS\Binn.

Note Note

The procedure described in this topic requires that the DelayValidation property of the Data Flow task and of any parent objects be set to its default value of False.

This procedure demonstrates how to develop a client application in managed code that loads the output of a package with a DataReader destination directly from memory. The steps summarized here are demonstrated in the code sample that follows.

To load data package output into a client application

  1. In the package, configure a DataReader destination to receive the output that you want to read into the client application. Give the DataReader destination a descriptive name, since you will use this name later in your client application. Make a note of the name of the DataReader destination.

  2. In the development project, set a reference to the Microsoft.SqlServer.Dts.DtsClient namespace by locating the assembly Microsoft.SqlServer.Dts.DtsClient.dll. By default, this assembly is installed in C:\Program Files\Microsoft SQL Server\100\DTS\Binn. Import the namespace into your code by using the C# Using or the Visual Basic Imports statement.

  3. In your code, create an object of type DtsClient.DtsConnection with a connection string that contains the command-line parameters required by dtexec.exe to run the package. For more information, see dtexec Utility. Then open the connection with this connection string. You can also use the dtexecui utility to create the required connection string visually.

    Note Note

    The sample code demonstrates loading the package from the file system by using the /FILE <path and filename> syntax. However you can also load the package from the MSDB database by using the /SQL <package name> syntax, or from the Integration Services package store by using the /DTS \<folder name>\<package name> syntax.

  4. Create an object of type DtsClient.DtsCommand that uses the previously created DtsConnection and set its CommandText property to the name of the DataReader destination in the package. Then call the ExecuteReader method of the command object to load the package results into a new DataReader.

  5. Optionally, you can indirectly parameterize the output of the package by using the collection of DtsDataParameter objects on the DtsCommand object to pass values to variables defined in the package. Within the package, you can use these variables as query parameters or in expressions to affect the results returned to the DataReader destination. You must define these variables in the package in the DtsClient namespace before you can use them with the DtsDataParameter object from a client application. (You may need to click the Choose Variable Columns toolbar button in the Variables window to display the Namespace column.) In your client code, when you add a DtsDataParameter to the Parameters collection of the DtsCommand, omit the DtsClient namespace reference from the variable name. For example:

    command.Parameters.Add(new DtsDataParameter("MyVariable", 1));
    
  6. Call the Read method of the DataReader repeatedly as needed to loop through the rows of output data. Use the data, or save the data for later use, in the client application.

    Important note Important

    The Read method of this implementation of the DataReader returns true one more time after the last row of data has been read. This makes it difficult to use the usual code that loops through the DataReader while Read returns true. If your code attempts to close the DataReader or the connection after reading the expected number of rows, without an additional, final call to the Read method, the code will raise an unhandled exception. However, if your code attempts to read data on this final iteration through a loop, when Read still returns true but the last row has been passed, the code will raise an unhandled ApplicationException with the message, "The SSIS IDataReader is past the end of the resultset." This behavior is different from that of other DataReader implementations. Therefore, when using a loop to read through the rows in the DataReader while Read returns true, you need to write code to catch, test, and discard this anticipated ApplicationException on the last successful call to the Read method. Or, if you know in advance the number of rows expected, you can process the rows, and then call the Read method one more time before closing the DataReader and the connection.

  7. Call the Dispose method of the DtsCommand object. This is particularly important if you have used any DtsDataParameter objects.

  8. Close the DataReader and the connection objects.

The following example runs a package that calculates a single aggregate value and saves the value to a DataReader destination, and then reads this value from the DataReader and displays the value in a text box on a Windows Form.

The use of parameters is not required when loading the output of a package into a client application. If you do not want to use a parameter, you can omit the use of the variable in the DtsClient namespace, and omit the code that uses the DtsDataParameter object.

To create the test package

  1. Create a new Integration Services package. The sample code uses "DtsClientWParamPkg.dtsx" as the name of the package.

  2. Add a variable of type String in the DtsClient namespace. The sample code use Country as the name of the variable. (You may need to click the Choose Variable Columns toolbar button in the Variables window to display the Namespace column.)

  3. Add an OLE DB connection manager that connects to the AdventureWorks2012 sample database.

  4. Add a data flow task to the package and switch to the Data Flow design surface.

  5. Add an OLE DB source to the data flow and configure it to use the OLE DB connection manager created previously, and the following SQL command:

    SELECT * FROM Sales.vIndividualCustomer WHERE CountryRegionName = ?
    
  6. Click Parameters and, in the Set Query Parameters dialog box, map the single input parameter in the query, Parameter0, to the DtsClient::Country variable.

  7. Add an Aggregate transformation to the data flow, and connect the output of the OLE DB source to the transformation. Open the Aggregate Transformation Editor and configure it to peform a "Count all" operation on all input columns (*) and to output the aggregated value with the alias CustomerCount.

  8. Add a DataReader destination to the data flow and connect the output of the Aggregate transformation to the DataReader destination. The sample code uses "DataReaderDest" as the name of the DataReader. Select the single available input column, CustomerCount, for the destination.

  9. Save the package. The test application created next will run the package and retrieve its output directly from memory.

To create the test application

  1. Create a new Windows Forms application.

  2. Add a reference to the Microsoft.SqlServer.Dts.DtsClient namespace by browsing to the assembly of the same name in %ProgramFiles%\Microsoft SQL Server\100\DTS\Binn.

  3. Copy and paste the following sample code into the code module for the form.

  4. Modify the value of the dtexecArgs variable as required so that it contains the command-line parameters required by dtexec.exe to run the package. The sample code loads the package from the file system.

  5. Modify the value of the dataReaderName variable as required so that it contains the name of the DataReader destination in the package.

  6. Put a button and a text box on the form. The sample code uses btnRun as the name of the button, and txtResults as the name of the text box.

  7. Run the application and click the button. After a brief pause while the package runs, you should see the aggregate value calculated by the package (the count of customers in Canada) displayed in the text box on the form.

Sample Code

using System;
using System.Windows.Forms;
using System.Data;
using Microsoft.SqlServer.Dts.DtsClient;

namespace DtsClientWParamCS
{
  public partial class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();
      this.btnRun.Click += new System.EventHandler(this.btnRun_Click);
    }

    private void btnRun_Click(object sender, EventArgs e)
    {
      string dtexecArgs;
      string dataReaderName;
      string countryName;

      DtsConnection dtsConnection;
      DtsCommand dtsCommand;
      IDataReader dtsDataReader;
      DtsDataParameter dtsParameter;

      Cursor.Current = Cursors.WaitCursor;

      dtexecArgs = @"/FILE ""C:\...\DtsClientWParamPkg.dtsx""";
      dataReaderName = "DataReaderDest";
      countryName = "Canada";

      dtsConnection = new DtsConnection();
      {
        dtsConnection.ConnectionString = dtexecArgs;
        dtsConnection.Open();
      }

      dtsCommand = new DtsCommand(dtsConnection);
      dtsCommand.CommandText = dataReaderName;

      dtsParameter = new DtsDataParameter("Country", DbType.String);
      dtsParameter.Direction = ParameterDirection.Input;
      dtsCommand.Parameters.Add(dtsParameter);

      dtsParameter.Value = countryName;

      dtsDataReader = dtsCommand.ExecuteReader(CommandBehavior.Default);

      {
        dtsDataReader.Read();
        txtResults.Text = dtsDataReader.GetInt32(0).ToString("N0");
      }

      //After reaching the end of data rows,
      // call the Read method one more time.
      try
      {
        dtsDataReader.Read();
      }
      catch (Exception ex)
      {
        MessageBox.Show(
          "Exception on final call to Read method:\n" + ex.Message + "\n" + ex.InnerException.Message,
          "Exception on final call to Read method", MessageBoxButtons.OK, MessageBoxIcon.Error);
      }

      // The following method is a best practice, and is
      //  required when using DtsDataParameter objects.
      dtsCommand.Dispose();

      try
      {
        dtsDataReader.Close();
      }
      catch (Exception ex)
      {
        MessageBox.Show(
          "Exception closing DataReader:\n" + ex.Message + "\n" + ex.InnerException.Message,
          "Exception closing DataReader", MessageBoxButtons.OK, MessageBoxIcon.Error);
      }

      try
      {
        dtsConnection.Close();
      }
      catch (Exception ex)
      {
        MessageBox.Show(
          "Exception closing connection:\n" + ex.Message + "\n" + ex.InnerException.Message,
          "Exception closing connection", MessageBoxButtons.OK, MessageBoxIcon.Error);
      }

      Cursor.Current = Cursors.Default;

    }
  }
}
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