LogProvider.SetExpression Method

public void SetExpression(
	string propertyName,
	string expression
)

using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.SqlServer.Dts.Runtime;

namespace LogProvider_Expression_Tests
{
    class Program
    {
        static void Main(string[] args)
        {
            // The package is one of the SSIS Samples. The package was
            // modified to log to the SSIS log provider for Text files
            // and saved before loading into this code.

            string mySample = @"C:\Program Files\Microsoft SQL Server\100\Samples\Integration Services\Package Samples\ExecuteProcess Sample\ExecuteProcess\UsingExecuteProcess.dtsx";

            // Create the Application, and load the sample.
            Application app = new Application();
            Package pkg = app.LoadPackage(mySample, null);

            // Get the LogProviders collection.
            LogProviders logProvs = pkg.LogProviders;

            // Get the "SSIS log provider for Text files"
            // provider from the collection.
            LogProvider textLogProv = logProvs["SSIS log provider for Text files"];

            //Display the current description of this provider.
            String currDescription = textLogProv.Description;
            Console.WriteLine("Current description: {0}", currDescription);

            // Set an expression. Only a few properties
            // are available to have expressions. For Log Providers, 
            //current only the properties of ConfigString, Description,
            // and Name take expressions.
            DateTime dt = DateTime.Now;
            String nowMonth = dt.ToString("m");
            String newDesc = "\"This is the log for " + nowMonth + "\"";
            textLogProv.SetExpression("Description", newDesc);

            // Validate the package to set the expression
            // onto the property.
            Connections pkgConns = pkg.Connections;          
            DTSExecResult valResult = pkg.Validate(pkgConns, null, null, null);
            if (valResult != DTSExecResult.Failure)
            {
                Console.WriteLine("Validation passed: {0}", valResult);
            }
            else
                Console.WriteLine("Validation FAILED: {0}", valResult);

            // Retrieve the log provider collections.
            logProvs = pkg.LogProviders;

            // Retreive the text log provider from the collection.
            textLogProv = logProvs["SSIS log provider for Text files"];

            // Check the expression, and verify that the name changed.
            String logProvExpr = textLogProv.GetExpression("Description");
            Console.WriteLine("The expression for Description is {0}", logProvExpr);
            String newDescAfter = textLogProv.Description;
            Console.WriteLine("The description is now: {0}", newDescAfter);
        }
    }
}