How can I change image visibility which is in mainwindow from another Window in WPF

Hi Nehal,
you can use Binding to Property in DataContext. Changing the value of this property and notify this the Visibility will be changed, For demonstration try following demo:

XAML MainWindow:

<Window x:Class="WpfApp1.Window002"  
        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:WpfApp002"  
        mc:Ignorable="d"  
        Title="Window002" Height="450" Width="800">  
  <Window.DataContext>  
    <local:ViewModel/>  
  </Window.DataContext>  
  <Grid>  
    <Grid.RowDefinitions>  
      <RowDefinition Height="auto"/>  
      <RowDefinition/>  
    </Grid.RowDefinitions>  
    <Grid Grid.Row="0" Background="LightGreen">  
      <Button Content="Add Url" Command="{Binding}" CommandParameter="AddUrl"  HorizontalAlignment="Left" Width="100" Margin="5"/>  
    </Grid>  
    <Grid Grid.Row="1">  
      <Image Source="/Images/no_files.png" Width="100" Height="100" Visibility="{Binding VisibilityOfPicture}"/>  
    </Grid>  
  </Grid>  
</Window>  

XAML secondary Window:

<Window x:Class="WpfApp1.Window002A"  
        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:WpfApp1"  
        mc:Ignorable="d"  
        Title="Add URL" Height="140" Width="500">  
  <Grid>  
    <Grid.ColumnDefinitions>  
      <ColumnDefinition Width="100"/>  
      <ColumnDefinition/>  
    </Grid.ColumnDefinitions>  
    <Grid.RowDefinitions>  
      <RowDefinition Height="50"/>  
      <RowDefinition/>  
    </Grid.RowDefinitions>  
    <Label Grid.Row="0" Grid.Column="0" Content="Add URL:" HorizontalAlignment="Center" VerticalAlignment="Center"/>  
    <TextBox Grid.Row="0" Grid.Column="2" Height="30" Margin="10"/>  
    <StackPanel Grid.Row="1" Grid.Column="2"  Orientation="Horizontal">  
      <Button Content="Check" Margin="10" Command="{Binding}" CommandParameter="Check" Width="80"/>  
      <Button Content="Download" Margin="10" Command="{Binding}" CommandParameter="Download" Width="80"/>  
    </StackPanel>  
  </Grid>  
</Window>  

and ViewModel class:

using System;  
using System.ComponentModel;  
using System.Runtime.CompilerServices;  
using System.Windows;  
using System.Windows.Input;  
using WpfApp1;  
  
namespace WpfApp002  
{  
  public class ViewModel : ICommand, INotifyPropertyChanged  
  {  
    public Visibility VisibilityOfPicture { get; set; } = Visibility.Visible;  
  
    public void Execute(object? parameter)  
    {  
      if (parameter == null) return;  
      switch (parameter.ToString())  
      {  
        case "AddUrl":  
          Window002A wnd = new Window002A();  
          wnd.DataContext = this;  
          wnd.ShowDialog();  
          break;  
        case "Check":  
          VisibilityOfPicture = Visibility.Hidden;  
          OnPropertyChanged(nameof(VisibilityOfPicture));  
          break;  
        case "Download":  
  
          break;  
        default:  
          break;  
      }  
    }   
    public event EventHandler? CanExecuteChanged;  
    public bool CanExecute(object? parameter) => true;  
  
    public event PropertyChangedEventHandler PropertyChanged;  
    private void OnPropertyChanged([CallerMemberName] string propName = "") => PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propName));  
  }  
}  

Result: