How resize whole window when I drag window with mouse - wpf

Question

I'm new with WPF controls, before I worked with WinForms applications, and there if I put anchor on control and put dock on container all works smoothly but here I have struggle where I mistake?
<Window x:Class="ChatApp.Client.ClientWindow"
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:ChatApp.Client"
mc:Ignorable="d"
Title="Client" Height="450" Width="800">
<Grid>
<DockPanel HorizontalAlignment="Stretch" VerticalAlignment="Stretch">
<StackPanel DockPanel.Dock="Top" Orientation="Horizontal" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
<GroupBox Header="Client" Height="Auto">
<StackPanel Orientation="Horizontal">
<TextBlock Margin="5, 0, 5, 0">Address:</TextBlock>
<TextBox x:Name="txtAddress" Width="80"></TextBox>
<TextBlock Margin="10, 0, 5, 0">Port:</TextBlock>
<TextBox x:Name="txtPort" Width="80"></TextBox>
<Button x:Name="btnConnect" Margin="430, 0, 5, 0" Content="Connect" Width="80" Click="btnConnect_Click"/>
</StackPanel>
</GroupBox>
</StackPanel>
<StackPanel DockPanel.Dock="Left" Orientation="Horizontal" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
<GroupBox Header="Chat" Width="650" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
<TextBox x:Name="txtConversation" AcceptsReturn="True"></TextBox>
</GroupBox>
</StackPanel>
<StackPanel DockPanel.Dock="Right" Orientation="Horizontal" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
<GroupBox Header="Users" Width="135" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
<ListBox x:Name="lbUsers" Height="Auto" Margin="5,0" VerticalAlignment="Stretch">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</GroupBox>
</StackPanel>
</DockPanel>
</Grid>
</Window>
I have three group box top dock, second left dock and last one is for right dock.
When I want to resize form with mouse right group box doesn't want to stretch when
I resize form.

Answer 1

Your layout seems very over complicated - are you just trying to clone what you did in Winforms in WPF?
It doesn't make any sense to have StackPanels or a Grid with only one child control each.
Try replacing your DockPanel with appropriately sized Grid Rows and Columns.
The GroupBoxes won't resize if you hard code their widths.
There's no need to define an ItemTemplate for the ListBox just to display a single string.
Something like the following would be a good starting point for your layout.
<Grid>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="*" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="4*" />
<ColumnDefinition Width="*" MinWidth="135" />
</Grid.ColumnDefinitions>
<GroupBox Header="Client" Grid.Row="0" Grid.Column="0" Grid.ColumnSpan="2" Margin="5">
<Grid >
<Grid.ColumnDefinitions>
<ColumnDefinition Width="Auto" />
<ColumnDefinition Width="*" />
<ColumnDefinition Width="Auto" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
<RowDefinition Height="Auto" />
</Grid.RowDefinitions>
<TextBlock Grid.Row="0" Grid.Column="0" Text="Address:"/>
<TextBox x:Name="txtAddress" Width="80" Grid.Row="1" Grid.Column="0" />
<TextBlock Grid.Row="2" Grid.Column="0" Text="Port:" />
<TextBox x:Name="txtPort" Width="80" Grid.Row="3" Grid.Column="0" />
<Button x:Name="btnConnect" Grid.Row="0" Grid.Column="2" Content="Connect" Width="80" />
</Grid>
</GroupBox>
<GroupBox Header="Chat" Grid.Row="1" Grid.Column="0" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
<TextBox x:Name="txtConversation" AcceptsReturn="True" />
</GroupBox>
<GroupBox Header="Users" Grid.Row="1" Grid.Column="1" VerticalAlignment="Stretch" HorizontalAlignment="Stretch">
<ListBox x:Name="lbUsers" />
</GroupBox>
</Grid>