If any one of have problem compiling the SharePoint 2010 Workflow (Sequential and State Machine) in you Dev Server. And if the Error is this
http://social.technet.microsoft.com/Forums/en-US/sharepoint2010programming/thread/74975cb4-20f9-4a3f-bb41-74382eecc5bb/#dd666781-46fb-4bb2-b8e8-cf49a4ebfa4b
Even for the empty workflow its giving this error.
Error 1
The "CompileWorkflowTask" task failed unexpectedly.
System.NotSupportedException: The given path's format is not supported.
at System.Security.Util.StringExpressionSet.CanonicalizePath(String path, Boolean needFullPath)
at System.Security.Util.StringExpressionSet.CreateListFromExpressions(String[] str, Boolean needFullPath)
at System.Security.Permissions.FileIOPermission.AddPathList(FileIOPermissionAccess access, AccessControlActions control, String[] pathListOrig, Boolean checkForDuplicates, Boolean needFullPath, Boolean copyPathList)
at System.Security.Permissions.FileIOPermission..ctor(FileIOPermissionAccess access, String[] pathList, Boolean checkForDuplicates, Boolean needFullPath)
at System.IO.Path.GetFullPath(String path)
at System.CodeDom.Compiler.TempFileCollection.EnsureTempNameCreated()
at System.CodeDom.Compiler.TempFileCollection.AddExtension(String fileExtension, Boolean keepFile)
at System.Workflow.ComponentModel.Compiler.CompileWorkflowTask.Execute()
at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask, Boolean& taskResult) stateWorkflow1
System.NotSupportedException: The given path's format is not supported.
at System.Security.Util.StringExpressionSet.CanonicalizePath(String path, Boolean needFullPath)
at System.Security.Util.StringExpressionSet.CreateListFromExpressions(String[] str, Boolean needFullPath)
at System.Security.Permissions.FileIOPermission.AddPathList(FileIOPermissionAccess access, AccessControlActions control, String[] pathListOrig, Boolean checkForDuplicates, Boolean needFullPath, Boolean copyPathList)
at System.Security.Permissions.FileIOPermission..ctor(FileIOPermissionAccess access, String[] pathList, Boolean checkForDuplicates, Boolean needFullPath)
at System.IO.Path.GetFullPath(String path)
at System.CodeDom.Compiler.TempFileCollection.EnsureTempNameCreated()
at System.CodeDom.Compiler.TempFileCollection.AddExtension(String fileExtension, Boolean keepFile)
at System.Workflow.ComponentModel.Compiler.CompileWorkflowTask.Execute()
at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask, Boolean& taskResult) stateWorkflow1
Check this Thread in MSDN Forum.
http://social.technet.microsoft.com/Forums/en-US/sharepoint2010programming/thread/74975cb4-20f9-4a3f-bb41-74382eecc5bb/#dd666781-46fb-4bb2-b8e8-cf49a4ebfa4b