No change in Xaml, change required in code, the way the stackpanel is used as below:
private void button1_Click(object sender, RoutedEventArgs e)
{
int y = 10;
int row = Convert.ToInt32(textBox1.Text);
int col = row;
int count = 0;
for (int i = 0; i < row; i++)
{
StackPanel txtbox = new StackPanel();
txtbox.Orientation = Orientation.Horizontal;
txtbox.Height = 23;
int x = 10;
for(int j = 0; j < col; j++)
{
TextBox txt = new TextBox();
txt.Width = 75;
txt.Name = "tb" + count;
count++;
x = x + 70;
txtbox.Children.Add(txt);
}
TxtStack.Children.Add(txtbox);
y = y + 25;
}
}