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PODataAdapter.Fill() behavior for row deleted at the data source
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  1. PODataAdapter.Fill() behavior for row deleted at the data source
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    copied!<p>I'm using the <code>DataSet</code>/<code>DataTable</code>/<code>DataAdapter</code> architecture to mediate between the database and my model objects, which have their own backing (they aren't backed by a DataRow). I've got a <code>DataAdapter</code> with <code>AcceptChangesDuringFill = False</code>, <code>AcceptChangesDuringUpdate = False</code>, and <code>FillLoadOption = OverwriteChanges</code>. Here's my understanding of the <code>DataAdapter</code> model under these conditions:</p> <h2>DataAdapter.Update()</h2> <ul> <li><code>DataRowState.Added</code> will result in the <code>InsertCommand</code> firing</li> <li><code>DataRowState.Modified</code> will result in the <code>UpdateCommand</code> firing</li> <li><code>DataRowState.Deleted</code> will result in the <code>DeleteCommand</code> firing</li> </ul> <h2>DataAdapter.Fill()</h2> <ul> <li>Any row in the returned result set whose primary key corresponds to an existing row in the <code>DataTable</code> will be used to update that row, and that row's state will always become <code>DataRowState.Modified</code>, <em>even if the returned row is identical to the current row</em></li> <li>Any row in the returned result set whose primary key doesn't correspond to any existing row will be used to create a new row, and that row's state will become <code>DataRowState.Added</code></li> <li>Any row in the <code>DataTable</code> that doesn't correspond to a row in the returned result set will stay at <code>DataRowState.Unchanged</code></li> </ul> <p>Given that I'm correct with this mental model, suppose I want to use <code>Fill()</code> to notice deleted rows in the data source. Also, suppose that the parameters of the <code>SelectCommand</code> don't return the entire table. I'm guessing that I have two options:</p> <ul> <li>Find all the rows that should've been updated by the <code>Fill()</code> but are still <code>DataRowState.Unchanged</code> (relies on my untested italicized assumption above). These rows have been deleted at the data source.</li> <li>Clear all relevant rows from the <code>DataTable</code> before the <code>Fill()</code>; any row that doesn't show up again has been deleted at the data source. This loses the distinction between <code>DataRowState.Added</code> and <code>DataRowState.Modified</code> that is preserved with the first method.</li> </ul> <p>So, my questions:</p> <ul> <li>Is my above model of the <code>DataAdapter</code> correct, subject to the property values I noted at the top?</li> <li>Which option should I go with to find deleted rows? I'd prefer the first one, but that relies on my assumption that all returned rows will be set to <code>DataRowState.Modified</code> even if the row is identical; is that a safe assumption?</li> <li>Am I going about this all wrong?</li> </ul>
 

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