XAML
<Window x:Class="ControlTest.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:ControlTest"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <StackPanel Width="100" x:Name="spMain">
        <Button />
        <Button />
        <Button />
        <Label Content="Yo." />
        <Button />
        <Button />
        <Button />
    </StackPanel>
</Window>

Code
using System;
using System.Windows;
using System.Windows.Controls;

namespace ControlTest
{
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            Random random = new Random();
            foreach (object x in spMain.Children)
            {
                if (x is Button button)
                {
                    button.Content = Math.Floor(random.NextDouble() * 25);
                }
            }
        }
    }
}