Fixed wrong behavior with the DataGrid

Lab/Exercise1/01-Start/ContosoExpenses/ContosoExpenses/ExpensesList.xaml

@@ -35,7 +35,13 @@
             <TextBlock x:Name="txtEmail" FontSize="16" Margin="5, 0, 0, 0" />
         </StackPanel>
         
-        <DataGrid x:Name="ExpensesGrid" SelectionChanged="OnSelectedExpense" AutoGenerateColumns="False" Grid.Row="4" Margin="0, 12, 0, 0">
+        <DataGrid x:Name="ExpensesGrid" 
+                  SelectionChanged="OnSelectedExpense" 
+                  AutoGenerateColumns="False" 
+                  IsReadOnly="True"
+                  Grid.Row="4" 
+                  Margin="0, 12, 0, 0" 
+                  SelectionMode="Single">
             <DataGrid.Columns>
                 <DataGridTextColumn Header="Date" Binding="{Binding Path=Date}" />
                 <DataGridTextColumn Header="Type" Binding="{Binding Path=Type}" />

Lab/Exercise1/01-Start/ContosoExpenses/ContosoExpenses/ExpensesList.xaml.cs

@@ -32,12 +32,15 @@ namespace ContosoExpenses
 
         private void OnSelectedExpense(object sender, SelectionChangedEventArgs e)
         {
-            var expense = e.AddedItems[0] as Expense;
-            if (expense != null)
+            if (e.AddedItems.Count > 0)
             {
-                ExpenseDetail detail = new ExpenseDetail();
-                detail.SelectedExpense = expense;
-                detail.ShowDialog();
+                var expense = e.AddedItems[0] as Expense;
+                if (expense != null && expense.ExpenseId != 0)
+                {
+                    ExpenseDetail detail = new ExpenseDetail();
+                    detail.SelectedExpense = expense;
+                    detail.ShowDialog();
+                }
             }
         }
 

Lab/Exercise1/01-Start/ContosoExpenses/ContosoExpenses/MainWindow.xaml

@@ -20,6 +20,8 @@
         </Menu>
 
         <DataGrid x:Name="CustomersGrid" SelectionChanged="OnSelectedEmployee" Grid.Row="1" AutoGenerateColumns="False"
+                  SelectionMode="Single"
+                  IsReadOnly="True"
                   Background="{StaticResource SemiTransparentBackground}" 
                   RowBackground="{StaticResource SemiTransparentBackground}"
                   ColumnHeaderStyle="{StaticResource DataGridHeaderStyle}"

Lab/Exercise1/01-Start/ContosoExpenses/ContosoExpenses/MainWindow.xaml.cs

@@ -32,12 +32,15 @@ namespace ContosoExpenses
 
         private void OnSelectedEmployee(object sender, SelectionChangedEventArgs e)
         {
-            var employee = e.AddedItems[0] as Employee;
-            if (employee != null)
+            if (e.AddedItems.Count > 0)
             {
-                ExpensesList detail = new ExpensesList();
-                detail.EmployeeId = employee.EmployeeId;
-                detail.Show();
+                var employee = e.AddedItems[0] as Employee;
+                if (employee != null && employee.EmployeeId != 0)
+                {
+                    ExpensesList detail = new ExpensesList();
+                    detail.EmployeeId = employee.EmployeeId;
+                    detail.Show();
+                }
             }
         }