how to refresh the gridiview in asp.net using c#

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C#

when i click the Show button, from the room table,In Gridview records as follows


room1 course1 room2 course2

11 AFF 21 MFA
12 EFA 22 ROC
13 23 ERS
14 SFU 24 ASM


Then i have save button when i click the save button records are saved in the Allocation Table.


The Allocation Table records as follows

room1 course1 room2 course2

11 AFF 21 MFA
12 EFA 22 ROC
13 POL 23 ERS
14 SFU 24 ASM

Then i have one button called Refresh gridview, when i click that refresh gridview button in gridview records as follows from the allocation table


finally in gridview records as follows


11 AFF 21 MFA
12 EFA 22 ROC
13 POL 23 ERS
14 SFU 24 ASM

when i click the refresh gridview error shows as follows

A field or property with the name 'Room1' was not found on the selected data source.


what can i do?

please help me.

Rgds,
Narasiman P.