计算矩阵总和时发生错误

Question

用户输入矩阵的维数，程序应计算行，列的总和以及矩阵的总和。如果矩阵的尺寸相同，例如2x2 3x3 7x7，那么一切都很好。但是，如果是3x2 5x4 7x5矩阵，则会发生异常：createElement_pr_4.exe中出现了'System.NullReferenceException'类型的未处理异常

其他信息：对象引用不表示对象实例。

<Window x:Class="createElement_pr_4.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:createElement_pr_4" 
mc:Ignorable="d" 
Title="" Height="600" Width="1000">
    <Grid x:Name="Container">
        <TextBox HorizontalAlignment="Left" Height="23" TextWrapping="Wrap" Text="" VerticalAlignment="Top" Width="24" x:Name="HeightEl"/>
        <TextBox HorizontalAlignment="Left" Height="23" Margin="40,0,0,0" TextWrapping="Wrap" Text="" VerticalAlignment="Top" Width="28" x:Name="WidthEl"/>
        <Button Content="Создать таблицу" HorizontalAlignment="Left" Margin="92,0,0,0" VerticalAlignment="Top" Width="120" x:Name="Create" Click="Create_Click"/>
        <Button Content="Вычислить"  HorizontalAlignment="Left" Margin="61,178,0,0" VerticalAlignment="Top" Width="75" x:Name="Add" Click="Add_Click"/>
        <Label x:Name="test" Content="" HorizontalAlignment="Left" Margin="10,533,0,-7" VerticalAlignment="Top" Height="43" Width="120"/>
        <Label x:Name="row" Content="" HorizontalAlignment="Left" Margin="158,533,0,0" VerticalAlignment="Top" Width="377"/>
        <Label x:Name="col" Content="" HorizontalAlignment="Left" Margin="580,533,0,0" VerticalAlignment="Top" Width="377"/>
        <Label x:Name="label" Content="Общая сумма" HorizontalAlignment="Left" Margin="0,482,0,0" VerticalAlignment="Top"/>
        <Label x:Name="label1" Content="Сумма строк" HorizontalAlignment="Left" Margin="158,482,0,0" VerticalAlignment="Top"/>
        <Label x:Name="label2" Content="Сумма колонок" HorizontalAlignment="Left" Margin="580,482,0,0" VerticalAlignment="Top"/>





    </Grid>
</Window>

using System; 
using System.Collections.Generic; 
using System.Linq; 
using System.Text; 
using System.Threading.Tasks; 
using System.Windows; 
using System.Windows.Controls; 
using System.Windows.Data; 
using System.Windows.Documents; 
using System.Windows.Input; 
using System.Windows.Media; 
using System.Windows.Media.Imaging; 
using System.Windows.Navigation; 
using System.Windows.Shapes; 

namespace createElement_pr_4
{
    public partial class MainWindow : Window
    {
        int w, h;
        TextBox[,] textBoxes = new TextBox[10, 10];
        public MainWindow()
        {
            InitializeComponent();
        }

        private void Create_Click(object sender, RoutedEventArgs e)
        {
            foreach (var TextBoxItem in textBoxes)
            {
                Container.Children.Remove(TextBoxItem);
            }

            try
            {
                h = int.Parse(HeightEl.Text);
                if (h > 10)
                {
                    h = 0;
                    MessageBox.Show("error");
                }
                w = int.Parse(WidthEl.Text);
                if (w > 10)
                {
                    w = 0;
                    MessageBox.Show("error");
                }
            }
            catch (System.FormatException)
            {
                MessageBox.Show("error");
            }


            for (int i = 0; i < h; i++)
            {
                for (int j = 0; j < w; j++)
                {
                    TextBox textBox = new TextBox()
                    {
                        Height = 23,
                        Width = 23,
                        HorizontalAlignment = HorizontalAlignment.Left,
                        VerticalAlignment = VerticalAlignment.Top,
                        Margin = new Thickness(250.0 + (double)(j * 40), 100 + (double)(i * 40), 0, 0)
                    };
                    try
                    {
                        textBoxes[i, j] = textBox;
                        Container.Children.Add(textBoxes[i, j]);
                    }
                    catch (System.IndexOutOfRangeException)
                    {
                        MessageBox.Show("error");
                    }
                }
            }
            //Add.Visibility = Visibility.Visible;
            //Result.Visibility = Visibility.Visible;
        }

        private void Add_Click(object sender, RoutedEventArgs e)
        {
            try
            {
                double sumCol;
                double sumRow;
                double sumAll = 0;

                for (int j = 0; j < w; j++)
                {
                    sumCol = 0;
                    sumRow = 0;
                    for (int i = 0; i < h; i++)
                    {
                        sumAll += Convert.ToDouble((textBoxes[i, j]).Text);
                        sumCol += Convert.ToDouble((textBoxes[i, j]).Text);
                        sumRow += Convert.ToDouble((textBoxes[j, i]).Text);
                    }
                    col.Content += Convert.ToString(sumCol + ", ");
                    row.Content += Convert.ToString(sumRow + ", ");
                }
                test.Content = sumAll;
            }
            catch (System.FormatException)
            {
                MessageBox.Show("erroe");
            }
            catch (System.OverflowException)
            {
                MessageBox.Show("error");
            }

        }
    }
}