I tried to extract specific task from particular project to update the Resource/ Assignment. The following sample code is for my testing. I perform this in Console .NET framework and no error. Unfortunately, no changes happened in the Task assignment. The scenario will be, Task A was assigned to any personal named PERSON A, and now I want to add or change to another person named PERSON B. I have tried a lot of workarounds on this issue. But never work. If you have any solutions, please let me know, that will save more time for me. Thanks a lot once again.