Formatting datetime in workflows with custom workflow activity in Microsoft Dynamics CRM 4.0

I've found one weird thing in workflows - when you insert datetime value inside text field you can't format it. Result of such inserting:




I decided to develop custom activity which will give possibility to format those output.
This activity has two inputs - datetime value to format (CrmDateTime property) and format (string property) and one output - formatted datetime (string). Code of custom action:

using System;
using System.Text;
using System.Collections.Generic;
using System.Workflow.Activities;
using Microsoft.Crm.Workflow;
using System.Workflow.ComponentModel;
using Microsoft.Crm.Sdk;

namespace DateTimeFormatting
{
  [CrmWorkflowActivity("Formats date time with required format", "Formatting Routines")]
  public class FormatDateTime : SequenceActivity
  {
      protected override System.Workflow.ComponentModel.ActivityExecutionStatus Execute(System.Workflow.ComponentModel.ActivityExecutionContext executionContext)
      {
          string result = string.Empty;

          if (!string.IsNullOrEmpty(DateFormat) && datetime != null)
          {
              result =  DateTime.Parse(datetime.Value).ToString(DateFormat);
          }

          Result = result;

          return ActivityExecutionStatus.Closed;
      }

      public static DependencyProperty DateFormatProperty = DependencyProperty.Register("DateFormat", typeof(string), typeof(FormatDateTime));

      [CrmInput("Format of DateTime")]
      public string DateFormat
      {
          get
          {
              return (string)base.GetValue(DateFormatProperty);
          }
          set
          {
              base.SetValue(DateFormatProperty, value);
          }
      }

      public static DependencyProperty datetimeProperty = DependencyProperty.Register("datetime", typeof(CrmDateTime), typeof(FormatDateTime));

      [CrmInput("DateTime to format")]
      public CrmDateTime datetime
      {
          get
          {
              return (CrmDateTime)base.GetValue(datetimeProperty);
          }
          set
          {
              base.SetValue(datetimeProperty, value);
          }
      }

      public static DependencyProperty ResultProperty = DependencyProperty.Register("Result", typeof(string), typeof(FormatDateTime));

      [CrmOutput("Formatted DateTime")]
      public string Result
      {
          get
          {
              return (string)base.GetValue(ResultProperty);
          }
          set
          {
              base.SetValue(ResultProperty, value);
          }
      }

  }
}

Following screenshots show how to use this action:
1. Insert this action before using the result of formatting:


2. Click "Set Properties" button to insert datetime and format:


3. Fill "Format of DateTime" and "DateTime to Format" fields:


4. Add some workflow step formatted datetime to be used (for example sending email):





Save step and save and publish workflow. Result of work of this workflow:


Sourcecode: