How to use LINQ in a Workflow

Question

Can I use a LINQ Query such as the following in a Workflow?

private static void ShowQueryWithCode(IEnumerable<string> names)
{
    Console.WriteLine("Linq Query in Code - show names that start with 'R'");

    // Assuming there are no null entries in the names collection
    var query = from name in names where name.StartsWith("R") select name;

    // This is the same thing as 
    // var query = names.Where(name => name.StartsWith("R"));

    foreach (var name in query)
    {
        Console.WriteLine(name);
    }

    Console.WriteLine();
}

Answer

Yes, you can use LINQ with a Workflow in exactly the same way.

Download Sample Code

Step 1: Create a Workflow with an In Argument of type IEnumerable<string>

Here you can see that I've added the in argument

Step 2: Add a Variable for the query of type IEnumerable<string>

Before you can add a variable you need to include an activity which has variables.  In this workflow I've added a sequence.

Step 3: Assign the query the LINQ expression you want to use

You can use a method chain or query syntax.

Step 4: Iterate over the collection

In the completed workflow I used a ForEach<string> activity to iterate the list of names and write them to the console.

Summary

This example uses C# in .NET 4.5 but the same technique can be used with Visual Basic.

When you run it you can see that both methods work the same.

Happy Coding!

Ron Jacobs
http://blogs.msdn.com/rjacobs
Twitter: @ronljacobs