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}" />