DataGrid Value Change before update - WPF C# MVVM

Question

I'm trying to create CRUD using WPF C# MVVM. I have Document Type Master with script like below:

my XAML:

<TextBox Grid.Column="1"
                         materialDesign:HintAssist.FloatingOffset="0, -18"
                         IsReadOnly="False"
                         Style="{StaticResource MaterialDesignFloatingHintTextBox}"
                         materialDesign:HintAssist.Hint="Document Type"
                         HorizontalAlignment="Stretch"
                         FontSize="14"
                         Margin="0 10 0 20"
                         Text="{Binding Path=CurrentDocumentType.DocumentTypeName}" />

                <DataGrid x:Name="dgDocumentType"
                          CanUserAddRows="False"
                          SelectionUnit="FullRow"
                          SelectionMode="Extended"
                          AutoGenerateColumns="False"
                          IsReadOnly="True"
                          ItemsSource="{Binding Path=DocumentTypesList, Mode=TwoWay}"
                          SelectedItem="{Binding Path=SelectedDocumentType, Mode=TwoWay}">
                    <DataGrid.RowStyle>
                        <Style TargetType="{x:Type DataGridRow}">
                            <Setter Property="Foreground"
                                    Value="Black" />

                        </Style>
                    </DataGrid.RowStyle>

                    <DataGrid.Columns>
                        <DataGridTextColumn Header="ID"
                                            Binding="{Binding Path=IdDocumentType, Mode=TwoWay}"
                                            Visibility="Hidden" />
                        <DataGridTextColumn Header="Document Type"
                                            Binding="{Binding Path=DocumentTypeName, Mode=TwoWay}" />
                    </DataGrid.Columns>

                </DataGrid>

And this is my ViewModel:

 private DocumentType selectedDocumentType;

    public DocumentType SelectedDocumentType
    {
        get { return selectedDocumentType; }
        set
        {
            selectedDocumentType = value;
            CurrentDocumentType = selectedDocumentType;

            OnPropertyChanged("SelectedDocumentType");
            
        }
    }

    private DocumentType currentDocumentType;

    public DocumentType CurrentDocumentType
    {
        get { return currentDocumentType; }
        set
        {
            currentDocumentType = value;
            OnPropertyChanged("CurrentDocumentType");


        }
    }

i'm using CurrentDocumentType = selectedDocumentType; so my textbox always show selected value everytime row in datagrid selected.

The problem is everytime i try to change value in textbox currentDocument Type, selected item in datagrid changes too. i want value in datagrid change when i hit update button, any idea? thanks before.

preview image

Answer 1

Binding for TextBox is TwoWay by default. You need to change it to OneWay if you don't want to change the source.

<TextBox
    Grid.Column="1"
    materialDesign:HintAssist.FloatingOffset="0, -18"
    IsReadOnly="False"
    Style="{StaticResource MaterialDesignFloatingHintTextBox}"
    materialDesign:HintAssist.Hint="Document Type"
    HorizontalAlignment="Stretch"
    FontSize="14"
    Margin="0 10 0 20"
    Text="{Binding Path=CurrentDocumentType.DocumentTypeName, Mode=OneWay}" />