Accessing the MainWindow class tools by other c# classes

Question

I need to access textbox and label controls for other c# classes(not only MainWindow class) in wpf.

I used x:FieldModifier="public" but still negative.

Is it possible to populate MainWindow class Tools for other classes?

Here is my simplified example code:

 

<Window x:Class="MyAbsClass.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:MyAbsClass"

mc:Ignorable="d"

Title="MainWindow" Height="350" Width="525">

<Grid>

<TextBox x:FieldModifier="public" x:Name="txt1"/>

<TextBox x:FieldModifier="public" x:Name="txt2"/>

<Button x:FieldModifier="public" x:Name="btn1" Content="Button" Click="btn1_Click"/>

</Grid>

</Window>

 

namespace MyAbsClass

{

class manipulate

{

public void add()

{

int a=int32.Parse(txt1.Text);

int b=int32.Parse(txt2.Text);

}

}

public partial class MainWindow : Window

{

public MainWindow()

{

InitializeComponent();

}

private void btn1_Click(object sender, RoutedEventArgs e)

{

MessageBox.Show("Added value= "+(a+b));

}

}

}