no 'Unit' columns in dtPurchaseProductExp but the error show

forgive me if i am asking silly question

but i can't figure it out what is wrong

In save button, i update datatables to database

{

new SqlCommandBuilder(sa);

sa.Update(dtPurchaseProductExp);

new SqlCommandBuilder(sa1);

sa1.Update(dtPurchaseProduct);

}

i don't have 'Unit' columns in dtPurchaseProductExp but

the following error shows up

![enter image description here][1]

![these are data columns of PurcaseProduct][2]

![these are data columns of PurcaseProductExp][3]

[1]: http://i.stack.imgur.com/u6mvu.jpg

[2]: http://i.stack.imgur.com/TU7ML.jpg

[3]: http://i.stack.imgur.com/eYzeS.jpg