linq problem for selecting.

Hi I  have Got One Problem I am usinq wcf with linq 
There are two table CountryMaster and  state master. i have create assosiation The parent table  is State master and child table is CountryMaster. After Submit oN State Master Then Bind The Grid. I have Submitted The Value But When I bind GridView there is an error
Sequence contains more than one element
Plz Help me.
 
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