title: System.Windows.Data Error: 1 System.Windows.Data Error: 5
body: <p>All,</p>
  
  <p>I have a WPF app that has a DataGrid control bound to ItemsSource=MyContext.Entity1.Local (which is an ObservableCollection).
  Inside of this app is a DataGridComboBoxColumn as follows:</p>
  
  <pre><code>&lt;DataGridComboBoxColumn Header="User"
                          SelectedValueBinding="{Binding Path=USR_ID, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"
                          SelectedItemBinding="{Binding Path=TBL_USR, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"
                          ItemsSource="{Binding Path=MyEntity.TBL_USR, UpdateSourceTrigger=PropertyChanged, Source={StaticResource VM}}"
                          SelectedValuePath="USR_ID"
                          DisplayMemberPath="USR_WINLOGON" /&gt;
  </code></pre>
  
  <p>My problem is that I get the following error:</p>
  
  <pre><code>System.Windows.Data Error: 1 : Cannot create default converter to perform 'two-way' conversions between types MyContextType.TBL_USR' and 'System.String'. Consider using Converter property of Binding. BindingExpression:Path=TBL_USR; DataItem='Entity1Cl_4FDC0A147BE18671D96960BD8695EC4E3656B773570659474EE4FF228884E823' (HashCode=7143675); target element is 'DataGridCell' (Name=''); target property is 'CellContent' (type 'String')
  System.Windows.Data Error: 5 : Value produced by BindingExpression is not valid for target property.; Value='System.Data.Entity.DynamicProxies.TBL_USR30704B5EF5DAA11FBF2C9B305F529659FBCF422ED6696643EDB375A5D77F5A96' BindingExpression:Path=TBL_USR; DataItem='Entity1Cl_4FDC0A147BE18671D96960BD8695EC4E3656B773570659474EE4FF228884E823' (HashCode=7143675); target element is 'DataGridCell' (Name=''); target property is 'CellContent' (type 'String')
  </code></pre>
  
  <p>I figure it has something to do with DynamicProxies, but I can't figure out what's causing this (.Local?), and how to code around this (at least, not without using a TypeConverter and Reflection, yuck).</p>
  
  <p>It's either that, or something to do with WPF misbehaving (but I can't find anywhere in the above markup where I'm trying to set my entity as a string).</p>
  
  <p>So I ask, does anyone know how I can force Entity1.Local[n].TBL_USR to just be a TBL_USR, or if perhaps there's another way (without reflection) I could set my SelectedItemBinding?</p>
  
  <p>Thanks.</p>
  
  <p>I'm using EF 4.4 (Database First) and .Net 4.0.</p>