In WebGridRow class, there is a public property named “ForceNoEdit” that will suit with your scenario. “ForceNoEdit” determines whether this row will be forced to not allow editing. Enabling this property on row will force the corresponding row to be read-only. Below is the snippet code that shows how to enable a read-only row from server side event.

protected void productGrid_InitializeRow(object sender, ISNet.WebUI.WebGrid.RowEventArgs e)
{
    e.Row.ForceNoEdit = true;
}

You can also disabling row editing on client side event by invoking “SetForceNoEdit(parameter)” method of WebGridRow. The parameter has a Boolean value, true means Not Editable, false means Editable. Below is the snippet code that shows how to enable a read-only row from client side event.

selectedRow.SetForceNoEdit(forceNoEdit); // set the row as editable (false) or not editable (true)

For more detail, please check ProductCatalog.aspx and Client_ProgrammaticEdit.aspx reference sample in WebGridSamples project. Hope this helps.