Usage of the Switch Activity with Custom Types

This topic applies to Windows Workflow Foundation 4 (WF4).

This sample describes how to enable a Switch activity to evaluate a user-defined complex type at runtime. In most traditional procedural programming languages, a switch statement selects an execution logic based on the conditional evaluation of a variable. Traditionally, a switch statement operates on an expression that can be statically evaluated. For example, in C# this means that only primitive types, such as Boolean, Int32, String, and enumeration types are supported.

To enable switching on a custom class, logic must be implemented to evaluate values of the custom complex type at runtime. This sample demonstrates how to enable switching on a custom complex type named Person.

• In the custom class Person, a TypeConverter attribute is declared with the name of the custom TypeConverter.

  [TypeConverter(typeof(PersonConverter))]
  public class Person
  {
     public string Name { get; set; }
     public int Age { get; set; }
  ...
  

• In the custom class Person, the Equals and GetHashCode classes are overridden.

  public override bool Equals(object obj)
  {
      Person person = obj as Person;
  
      if (person != null)
      {
          return string.Equals(this.Name, person.Name);
      }
  
      return false;
  }
  
  public override int GetHashCode()
  {
      if (this.Name != null)
      {
          return this.Name.GetHashCode();
      }
  
      return 0;
  }
  

• A custom TypeConverter class is implemented that performs the conversion of an instance of the custom class to a string and a string to an instance of a custom class.

  public class PersonConverter : TypeConverter
  {
      public override bool CanConvertFrom(ITypeDescriptorContext context,
         Type sourceType)
      {
          return (sourceType is string);
      }
  
      // Overrides the ConvertFrom method of TypeConverter.
      public override object ConvertFrom(ITypeDescriptorContext context,
         CultureInfo culture, object value)
      {
          if (value == null)
          {
              return null;
          }
  
          if (value is string)
          {
              return new Person
              {
                  Name = (string)value
              };
          }
  
          return base.ConvertFrom(context, culture, value);
      }
  
      // Overrides the ConvertTo method of TypeConverter.
      public override object ConvertTo(ITypeDescriptorContext context,
         CultureInfo culture, object value, Type destinationType)
      {
          if (destinationType == typeof(string))
          {
              if (value != null)
              {
                  return ((Person) value).Name;
              }
              else
              {
                  return null;
              }
          }
  
          return base.ConvertTo(context, culture, value, destinationType);
      }
  }
  

The following files are included in this sample:

• Person.cs: Defines the Person class.

• PersonConverter.cs: The type converter for the Person class.

• Sequence.xaml: a workflow that switches over the Person type.

• Program.cs: The main function that runs the workflow.

To use this sample

1. Load Switch.sln in Visual Studio 2010.

2. Press CTRL+SHIFT+B to build the solution.

3. Press CTRL + F5 to run the sample.

Note:

The samples may already be installed on your computer. Check for the following (default) directory before continuing. <InstallDrive>:\WF_WCF_Samples If this directory does not exist, go to Windows Communication Foundation (WCF) and Windows Workflow Foundation (WF) Samples for .NET Framework 4 to download all Windows Communication Foundation (WCF) and WF samples. This sample is located in the following directory. <InstallDrive>:\WF_WCF_Samples\WF\Basic\Built-InActivities\Switch

See Also

Concepts

.NET Framework 4 Built-In Activity Library