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POLINQ many-to-many in WPF databinding path
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  1. POLINQ many-to-many in WPF databinding path
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    copied!<p>in my c# WPF app i add columns to a DataGrid at runtime, and populate from my SQL db via LINQ. this is working fine until i try to add data from my many-to-many table </p> <p>here's a simplified version of the 3 relevant tables my db:</p> <pre><code>documents: document_id, title documents_keywords: document_id, keyword_id, value keywords: keyword_id, name </code></pre> <p>what i want in my DataGrid is a column for document.title, plus a column for each record in document.documents_keywords based on user selection. here's my code:</p> <pre><code> DataGrid dataGrid = new DataGrid(); dataGrid.Columns.Add(new DataGridTextColumn { Header = "Title", Binding = new Binding("title") }); foreach (string keywordName in keywordsListBox.SelectedItems) { dataGrid.Columns.Add(new DataGridTextColumn { Header = keywordName, Binding = new Binding("documents_keywords.FirstOrDefault(kw =&gt; kw.keyword.name.Equals(\""+keywordName+"\")).value") }); } dataGrid.ItemsSource = from d in db.documents select d; </code></pre> <p>i'm getting the keyword headers, but the cells are all blank. the binding fails at FirstOrDefault:</p> <pre><code>System.Windows.Data Error: 40 : BindingExpression path error: 'FirstOrDefault(d_k =&gt; d_k.keyword.name.Equals("Order#"))' property not found on 'object' ''EntityCollection`1' (HashCode=7935090)'. BindingExpression:Path=documents_keywords.FirstOrDefault(d_k =&gt; d_k.keyword.name.Equals("Order#")).value; DataItem='document' (HashCode=5781744); target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String') </code></pre> <p>what is the best way to accomplish this? forgive me as this is my first jaunt into WPF and LINQ. </p>
 

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