<ToolboxBitmapAttribute(GetType(CreateTaskWithContentType), "Resources.CreateTaskWithContentType.bmp")> _
<ActivityToolboxDisplayAttribute("VSTTSharePointWorkflowTask", True)> _
Public NotInheritable Class CreateTaskWithContentType _
    Inherits CallExternalMethodActivity

Dim instance As CreateTaskWithContentType

[ToolboxBitmapAttribute(typeof(CreateTaskWithContentType), "Resources.CreateTaskWithContentType.bmp")]
[ActivityToolboxDisplayAttribute("VSTTSharePointWorkflowTask", true)]
public sealed class CreateTaskWithContentType : CallExternalMethodActivity

public static void VerifyModifyTaskList(SPList taskList, string contentType)
{
   try
   {
      SPContentTypeId contentTypeId = new  
      SPContentTypeId(contentType);
   taskList.ContentTypesEnabled = true;
                SPContentTypeId matchContentTypeId = taskList.ContentTypes.BestMatch(contentTypeId);
                if (matchContentTypeId.Parent.CompareTo(contentTypeId) != 0)
                {
                    SPContentType ct = taskList.ParentWeb.AvailableContentTypes[contentTypeId];
                    taskList.ContentTypes.Add(ct);
                    taskList.Update();
                }
            }
            catch
            {
                throw;
            }
        }