Code WPF Save To File

<Window x:Class="WpfApp7.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:WpfApp7"
        mc:Ignorable="d"
        Title="Save To File" Height="450" Width="800">

  <Grid>
    <Grid.RowDefinitions>
      <RowDefinition />
    </Grid.RowDefinitions>
    <Grid.ColumnDefinitions>
      <ColumnDefinition Width="*" />
      <ColumnDefinition Width="*" />
    </Grid.ColumnDefinitions>

    <Grid Grid.Column="0" Background="#FFAFAFAF">
      <Grid Margin="40,30,25,30">
        <Grid.RowDefinitions>
          <RowDefinition Height="*" />
          <RowDefinition Height="1.8*" />
          <RowDefinition Height="*" />
          <RowDefinition Height="1.8*" />
          <RowDefinition Height="*" />
          <RowDefinition Height="1.8*" />
          <RowDefinition Height="*" />
          <RowDefinition Height="3*" />
        </Grid.RowDefinitions>
        <TextBlock Grid.Row="0" FontSize="20">First Name</TextBlock>
        <TextBox Grid.Row="1" FontSize="35" Padding="10,0,0,0">Bruce</TextBox>
        <TextBlock Grid.Row="2" FontSize="20">Last Name</TextBlock>
        <TextBox Grid.Row="3" FontSize="35" Padding="10,0,0,0">Willis</TextBox>
        <TextBlock Grid.Row="4" FontSize="20" Text="Year of birth"/>
        <TextBox Grid.Row="5" FontSize="35" Padding="10,0,0,0">1955</TextBox>
        <Grid Grid.Row="7" Margin="0,12,0,10">
          <Grid.ColumnDefinitions>
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="*" />
            <ColumnDefinition Width="*" />
          </Grid.ColumnDefinitions>
          <Button Grid.Column="0" Content="Add" FontSize="30" Margin="10,0,10,0" />
          <Button Grid.Column="1" Content="Save" FontSize="30" Margin="10,0,10,0" />
          <Button Grid.Column="2" Content="Load" FontSize="30" Margin="10,0,10,0" />
        </Grid>
      </Grid>
    </Grid>
    <TextBox Grid.Column="1" Text="Tom Cruise 1962" FontSize="25" Padding="20,20,20,20" />
  </Grid>
</Window>