Retrieving task guid from dataset

hello forum members,

i am trying to assign resources to tasks and when i retrieve a task guid from dataset, I have conversion errors that i can't figure out. 

Here is my code for a task id : 

string taskId = projDs[0].Tables["Task"].Rows[0]["TASK_UID"].ToString();

newAssignmentRow.TASK_UID = new Guid(taskid); //error here. doesn't convert 

the error that i am getting is "cannot convert from System.Guid[] to System.Guid

Does anyone has any ideas? 

tatiana