WPF_WPF/MainWindow.xaml

<Window
        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:WpfApp2"
        xmlns:dxre="http://schemas.devexpress.com/winfx/2008/xaml/richedit" x:Class="WpfApp2.MainWindow"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800" MinWidth="800" MinHeight="450" FontFamily="Tahoma" FontSize="16">
    <StackPanel x:Name="StackPanel1" Orientation="Vertical">
        <StackPanel Orientation="Horizontal" UseLayoutRounding="False" Margin="0,0,0,40">
            <TextBox  Grid.ColumnSpan="2" Width="360"/>
            <ComboBox Name="ComboBox1" Grid.ColumnSpan="2" Width="200" Margin="10,0,0,0"></ComboBox>
            <ComboBox Grid.ColumnSpan="2" Width="200" Margin="10,0,0,0"></ComboBox>
        </StackPanel>
   
    </StackPanel>
</Window>