c# - The multi-part identifier "System.Data.DataRowView" could not be bound -

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i have table populate combobox1 , combobox1 should populate combobox2 , problem is. that's exception i'm getting

the multi-part identifier "system.data.datarowview" not bound.

code :

    private void frm2_load(object sender, eventargs e)     {         //populate combobox1         sqldataadapter da = new sqldataadapter("select categoryid, name categories", clsmain.con);         dataset ds = new dataset();         da.fill(ds);         combobox1.datasource = ds.tables[0];         combobox1.displaymember = "name";         combobox1.valuemember = "categoryid";     }      private void combobox1_selectedindexchanged(object sender, eventargs e)     {         //populate combobox2         sqldataadapter da = new sqldataadapter("select subcategoryid, name subcategories categoryid=" + combobox1.selectedvalue, clsmain.con);         dataset ds = new dataset();         da.fill(ds);         combobox2.datasource = ds.tables[0];         combobox2.displaymember = "name";         combobox2.valuemember = "subcategoryid";     } 

this due loading second combobox while filling data in first combo.
can avoid error by:
1. use selectionchangecommitted event instead of selectedindexchanged event.
or
2. detach selected index change event, populate combobox, attach event again as:

private void frm2_load(object sender, eventargs e) {    //detach event    combobox1.selectedindexchanged -= combobox1_selectedindexchanged;      //populate combobox1     sqldataadapter da = new sqldataadapter("select categoryid, name categories", clsmain.con);     dataset ds = new dataset();     da.fill(ds);     combobox1.datasource = ds.tables[0];     combobox1.displaymember = "name";     combobox1.valuemember = "categoryid";     //attach event again     combobox1.selectedindexchanged += combobox1_selectedindexchanged; } 

hopes you.