title: WPF Datagrid Cross row Validation
body: <p>Does anyone have any example on Cross row validation for WPF Datagrid. Cell level validation and Rowlevel validation doesn't fulfill my requirements. i am trying to stick with MVVM as much as possible. my last option is to use code behind. so basically i need to access the Itemssource when something happens in the grid. any help is much appreciated. 
  Thanks -Rey</p>