How to define a grid layout - layout

Question

I still do not manage to understand how define a flexible Grid layout...
Id like to have a Grid with n rows (i dont know how many) and m columns (i dont know how many).. I want cells have a specific height and width (50 and 50)....
This is how i can set row and column definition:
<Grid.ColumnDefinitions>
<ColumnDefinition Width="350" />
<ColumnDefinition Width="130" />
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto" />
<RowDefinition Height="2*" />
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
But in this way im just setting two columns and 3 rows... There is no way to set a Column definition and a row definition for each column and grid?
Thanx

Answer 1

Going on the initial question, this is how you can start C# :-
Grid Layout = new Grid();
foreach (your condition)
{
//
Layout.ColumnDefinitions.Add(new ColumnDefinition() { Width = GridLength.Auto });
Layout.ColumnDefinitions.Add(new ColumnDefinition() { Width = new GridLength(50)});
Layout.RowDefinitions.Add(new RowDefinition() { Height = new GridLength(50) });
}

Answer 2

This is how you do it
public MainPage()
{
InitializeComponent();
var def = new ColumnDefinition();
def.Width = new GridLength(100);
gdTest.ColumnDefinitions.Add(def);
StackPanel sp = new StackPanel();
sp.Background = new SolidColorBrush( Colors.Brown);
sp.SetValue(Grid.ColumnProperty, 1);
gdTest.Children.Add(sp);
}
Xaml
<Grid x:Name="gdTest" HorizontalAlignment="Stretch" VerticalAlignment="Stretch" Margin="5,0,5,0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<StackPanel Grid.Column="0" x:Name="TestStack" Background="Red"/>
</Grid>
add the code and test :)