In a datagrid , Instead of text box i got drop down list ,but how to fill it up with preloaded values
I hope you have created a template column and added dropdown to that.
Fine.
Whatever data you want to load to the dropdown, capture them in different rows(and first column) of a datatable say 'dtbSiteType'
Now , In the item command function of the datagrid, find that drop down list for each row of the datagrid in this way-
Note: 0 is the template cell number.
cmbSiteType = CType(e.Item.Cells(0).FindControl("cmbSiteType"), DropDownList)
With cmbSiteType
.DataSource = dtbSiteType
.DataBind()
End With