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POLINQ to SQL -
 

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    <p>I'm attempting to use LINQ to insert a record into a child table and I'm receiving a "Specified cast is not valid" error that has something to do w/ the keys involved. The stack trace is:</p> <blockquote> <p>Message: Specified cast is not valid.</p> <p>Type: System.InvalidCastException Source: System.Data.Linq TargetSite: Boolean TryCreateKeyFromValues(System.Object[], V ByRef) HelpLink: null Stack: at System.Data.Linq.IdentityManager.StandardIdentityManager.SingleKeyManager<code>2.TryCreateKeyFromValues(Object[] values, V&amp; v) at System.Data.Linq.IdentityManager.StandardIdentityManager.IdentityCache</code>2.Find(Object[] keyValues) at System.Data.Linq.IdentityManager.StandardIdentityManager.Find(MetaType type, Object[] keyValues) at System.Data.Linq.CommonDataServices.GetCachedObject(MetaType type, Object[] keyValues) at System.Data.Linq.ChangeProcessor.GetOtherItem(MetaAssociation assoc, Object instance) at System.Data.Linq.ChangeProcessor.BuildEdgeMaps() at System.Data.Linq.ChangeProcessor.SubmitChanges(ConflictMode failureMode) at System.Data.Linq.DataContext.SubmitChanges(ConflictMode failureMode) at System.Data.Linq.DataContext.SubmitChanges()</p> <p>(.....)</p> </blockquote> <p>This error is being thrown on the following code:</p> <pre><code> ResponseDataContext db = new ResponseDataContext(m_ConnectionString); CodebookVersion codebookVersion = db.CodebookVersions.Single(cv =&gt; cv.VersionTag == m_CodebookVersionTag); ResponseCode rc = new ResponseCode() { SurveyQuestionName = "Q11", Code = 3, Description = "Yet another code" }; codebookVersion.ResponseCodes.Add(rc); db.SubmitChanges(); //exception gets thrown here </code></pre> <p>The tables in question have a FK relationship between the two of them.<br> The parent table's column is called 'id', is the PK, and is of type: INT NOT NULL IDENTITY<br> The child table's column is called 'responseCodeTableId' and is of type: INT NOT NULL.</p> <p>codebookVersion (parent class) maps to table tblResponseCodeTable<br> responseCode (childClass) maps to table tblResponseCode</p> <p>If I execute SQL directly, it works. e.g. </p> <pre><code>INSERT INTO tblResponseCode (responseCodeTableId, surveyQuestionName, code, description) VALUES (13683, 'Q11', 3, 'Yet another code') </code></pre> <p>Updates to the same class work properly. e.g. </p> <pre><code>codebookVersion.ResponseCodes[0].Description = "BlahBlahBlah"; db.SubmitChanges(); //no exception - change is committed to db </code></pre> <p>I've examined the variable, rc, after the .Add() operation and it does, indeed, receive the proper responseCodeTableId, just as I would expect since I'm adding it to that collection.</p> <pre><code>tblResponseCodeTable's full definition: COLUMN_NAME TYPE_NAME id int identity responseCodeTableId int surveyQuestionName nvarchar code smallint description nvarchar dtCreate smalldatetime </code></pre> <p>dtCreate has a default value of GetDate().</p> <p>The only other bit of useful information that I can think of is that no SQL is ever tried against the database, so LINQ is blowing up before it ever tries (hence the error not being a SqlException). I've profiled and verified that no attempt is made to execute any statements on the database.</p> <p>I've read around and seen the problem when you have a relationship to a non PK field, but that doesn't fit my case.</p> <p>Can anyone shed any light on this situation for me? What incredibly obvious thing am I missing here? </p> <p>Many thanks.<br> Paul Prewett</p>
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