WPF Datagrid checkbox column checked

My datagrid checkbox column:

                    <DataGridTemplateColumn MaxWidth="45">
                    <DataGridTemplateColumn.CellTemplate>
                        <DataTemplate>
                            <CheckBox x:Name="check_tutar"  VerticalAlignment="Center" HorizontalAlignment="Center" HorizontalContentAlignment="Center" Checked="check_tutar_Checked"></CheckBox>
                        </DataTemplate>
                    </DataGridTemplateColumn.CellTemplate>
                </DataGridTemplateColumn>

I want to access this checkbox and change checked property. I try defalut method: check_tutar.IsChecked = false;

But didnt work because I can not access the checkbox using name. How can I change datagrid column checkbox checked property?