Update a data row inside an asp.net Data Grid View
<p>I think it would be easier for you to understand my problem if I explain the scenario a bit.</p>

<p>What I am doing is developing a system to a doctor using asp.net c#. For the creation of the prescription, I add a check box list for the list of medicines and submit button below it. When the submit button clicked selected check box list items added to the sql server database and show a data grid with the selected medicines in the same page.</p>

<p>In the data grid there are two columns for medicine name and dosage.Medicine name is taken from the database.I need to give the user the ability to enter the dosage through that grid view. I need to use update command because the record is already there in the sql server.But empty value in the dosage column.I tried to use update command in the data source control. But I can't figure out how to give the WHERE clause because I can't specify the database row which the updating record relate to.</p>

<p>I would be glad to hear some help from you. All the comments are welcome.</p>
