# System.Data.DuplicateNameException: A column named 'APPROVAL4\_dtVacationEndDate' already belongs to this DataTable

**URL:** <https://discuss.workflowgen.com/t/system-data-duplicatenameexception-a-column-named-approval4-dtvacationenddate-already-belongs-to-this-datatable/1799>\
**Category:** Web API\
**Created:** [February 1, 2021, 6:54pm UTC](https://discuss.workflowgen.com/t/system-data-duplicatenameexception-a-column-named-approval4-dtvacationenddate-already-belongs-to-this-datatable/1799 "2021-02-01T18:54:35Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Silini](https://avatars.discourse-cdn.com/v4/letter/s/5e9695/32.png) [@Silini](https://discuss.workflowgen.com/u/Silini)\
**Post date:** [February 1, 2021, 6:54pm UTC](https://discuss.workflowgen.com/t/system-data-duplicatenameexception-a-column-named-approval4-dtvacationenddate-already-belongs-to-this-datatable/1799/1 "2021-02-01T18:54:35Z")

</div>

Hi everybody.

I hope all doing well.  
last time I tried to apply an action to an activityInstance using wfgen web service as below:

POST /wfgen/ws/ProcessesRuntime.asmx/CompleteWebFormActivityInstance?impersonateusername=username HTTP/1.1

Host: 10.23.6.189

Content-Type: application/x-www-form-urlencoded; charset=utf-8

Content-Length: 586

processInstanceId=24857&activityInstanceId=7&workflowContext=APPROVAL4\_rbDecision4TEXT INOUTموافقةAPPROVAL4\_dtVacationEndDateDATETIMEINOUT2021-01-25T00:00:00+02:00APPROVAL4\_dtVacationStartDateDATETIMEINOUT2021-01-01T00:00:00+02:00

but I faced the below exception :

HTTP/1.1 500 Internal Server Error

System.Data.DuplicateNameException: A column named APPROVAL4\_dtVacationEndDate already belongs to this DataTable.  
I searched a lot in the forum and the web but I couldn’t find any answer.  
kindly may you advice me to fix this error.

thanks in advance.  
BR.