error showing cant implecitly convert coi to string

Question

My class file

public void JoinTab(string s)

{

var x = from n in db.EMPs

join d in db.DEPTs on n.EMPNO equals d.DEPTNO

select new { n.ENAME, d.DNAME };

}

===============

.aspx.cs file

 

Grid1.DataSource = x.ToList();

Grid1.DataSource = objrepo.JoinTab();

 

 

im getting erroe at  "objrepo.JoinTab();" cant implecitely convert voi to string