C-Sharp WPF MVVM ListView mit TextBox SelectionChanged Event

Point currentMouseOnGridPosition = Mouse.GetPosition(null);
double col1 = (_ListView.View as GridView).Columns[2].Width + 20;
double col2 = (_ListView.View as GridView).Columns[3].Width + 20;

if (currentMouseOnGridPosition.X < /* auch > versucht usw */ (col1 + col2))
{
        // viele Viele Versuche
}

<ListView
            x:Name="_ListView"  
            Grid.Row="9"  
            Grid.ColumnSpan="4"  
            x:FieldModifier="public"  
            AllowDrop="True"  
            AutomationProperties.IsColumnHeader="True"  
            ItemsSource="{Binding Path=List_All}"  
            KeyboardNavigation.TabNavigation="Continue"  
            SelectionChanged="_ListView_SelectionChanged"  
            SelectionMode="Multiple">  
            <ListView.View>
                <GridView>
                    <GridViewColumn
                        Width="80"  
                        DisplayMemberBinding="{Binding SectionName}"  
                        HeaderContainerStyle="{StaticResource GridViewHeaderAllignment}">  
                        <GridViewColumn.Header>
                            <TextBlock Text=" Section" />  
                        </GridViewColumn.Header>
                    </GridViewColumn>

                    <GridViewColumn
                        Width="auto"  
                        DisplayMemberBinding="{Binding ProgramName}"  
                        HeaderContainerStyle="{StaticResource GridViewHeaderAllignment}">  
                        <GridViewColumn.Header>
                            <TextBlock Text=" Programm-Name" />  
                        </GridViewColumn.Header>
                    </GridViewColumn>

                    <GridViewColumn Width="200" HeaderContainerStyle="{StaticResource GridViewHeaderAllignment}">  
                        <GridViewColumn.Header>
                            <TextBlock Text=" Registry-Key" />  
                        </GridViewColumn.Header>
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <TextBox
                                    Width="150"  
                                    HorizontalAlignment="Center"  
                                    IsEnabled="{Binding Path=SearchedRegKey_IsEnabled}"  
                                    Text="{Binding Path=SearchedRegKey, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />  
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                    </GridViewColumn>

                    <GridViewColumn Width="200" HeaderContainerStyle="{StaticResource GridViewHeaderAllignment}">  
                        <GridViewColumn.Header>
                            <TextBlock Text=" Display-Name" />  
                        </GridViewColumn.Header>
                        <GridViewColumn.CellTemplate>
                            <DataTemplate>
                                <TextBox
                                    Width="150"  
                                    HorizontalAlignment="Center"  
                                    IsEnabled="{Binding Path=SearchedDisplayName_IsEnabled}"  
                                    Text="{Binding Path=SearchedDisplayName, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />  
                            </DataTemplate>
                        </GridViewColumn.CellTemplate>
                    </GridViewColumn>
                </GridView>
            </ListView.View>
        </ListView>

private void _ListView_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
            foreach (ListView_Uninstall_Model item in e.AddedItems)
            {
                item.SearchedDisplayName_IsEnabled  = true;
                item.SearchedRegKey_IsEnabled       = true;
                item.SelectedAsStart                = true;
            }

            foreach (ListView_Uninstall_Model item in e.RemovedItems)
            {
                    item.SearchedDisplayName = string.Empty;
                    item.SearchedRegKey_IsEnabled = false;
                    item.SearchedRegKey = string.Empty;
                    item.SelectedAsStart = false;
            }
}