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PORetrieving values of ReadOnly fields from DynamicData DetailsView in Edit Mode on Updating using LinqDataSource
 

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  1. PORetrieving values of ReadOnly fields from DynamicData DetailsView in Edit Mode on Updating using LinqDataSource
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    <p>I have several tables in my database that have read-only fields that get set on Inserting and Updating, namely: AddDate (DateTime), AddUserName (string), LastModDate (DateTime), LastModUserName (string).</p> <p>All of the tables that have these values have been set to inherit from the following interface:</p> <pre><code>public interface IUserTrackTable { string AddUserName { get; set; } DateTime AddDate { get; set; } string LastModUserName { get; set; } DateTime LastModDate { get; set; } } </code></pre> <p>As such, I have the following method on the Edit.aspx page:</p> <pre><code>protected void DetailsDataSource_Updating(object sender, LinqDataSourceUpdateEventArgs e) { IUserTrackTable newObject = e.NewObject as IUserTrackTable; if (newObject != null) { newObject.LastModUserName = User.Identity.Name; newObject.LastModDate = DateTime.Now; } } </code></pre> <p>However, by the time it hits this method, the e.OriginalObject has already lost the values for all four fields, so a ChangeConflictException gets thrown during the actual Update. I have tried adding the four column names to the DetailsView1.DataKeyNames array in the Init event handler:</p> <pre><code>protected void Page_Init(object sender, EventArgs e) { // other things happen before this var readOnlyColumns = table.Columns.Where(c =&gt; c.Attributes.SingleOrDefaultOfType&lt;ReadOnlyAttribute&gt;(ReadOnlyAttribute.Default).IsReadOnly).Select(c =&gt; c.Name); DetailsView1.DataKeyNames = DetailsView1.DataKeyNames.Union&lt;string&gt;(readOnlyColumns).ToArray&lt;string&gt;(); DetailsView1.RowsGenerator = new CustomFieldGenerator(table, PageTemplates.Edit, false); // other things happen after this } </code></pre> <p>I've tried making that code only happen on PostBack, and still nothing. I'm at a lose for how to get the values for all of the columns to make the round-trip.</p> <p>The only thing the CustomFieldGenerator is handling the ReadOnlyAttribute, following the details on <a href="http://csharpbits.notaclue.net/2009/01/making-field-read-only-via.html" rel="nofollow">C# Bits</a>.</p> <p>UPDATE: After further investigation, the values make the round trip to the DetailsView_ItemUpdating event. All of the values are present in the e.OldValues dictionary. However, they are lost by the time it gets to the LinqDataSource_Updating event.</p> <p>Obviously, there are the "solutions" of making those columns not participate in Concurrency Checks or other ways that involve hard-coding, but the ideal solution would dynamically add the appropriate information where needed so that this stays as a Dynamic solution.</p>
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