title: wpf datagrid: Make cell Editable and non-Editable
body: <p>I have a datagrid with 2 columns one is DataGridComboBox namely 'Serial No' column and other is DataGridTextColumn namely 'Qty' .The DataGridComboBox column may or not having values in it.If the combobox has values then the user can select one value from it then the qty column become uneditable (readonly) and set 1 as default qty other wise it become editable cell ,Hence the user can enter any qty on it.How do I made the Qty column editable and non editable based on the value selection from combobox ?</p>