CanResize="false"

------解决方案--------------------
C# code

<Window x:Class="GetPosition.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:local="clr-namespace:GetPosition" ResizeMode="NoResize"
        Title="MainWindow" Height="350" Width="525">