Grid

Introduction

Grid is a container control that arranges children in rows and columns with independent sizing per row and per column. It is similar to WPF's Grid control and is well-suited for tabular layouts, form layouts, and any UI where rows and columns need different widths or heights.

Grid is an experimental control and its API may change in future releases.

Rows and columns are defined by adding RowDefinition and ColumnDefinition instances to the RowDefinitions and ColumnDefinitions collections. Children are placed into a specific cell by calling AddChild with a row and column index.

Code Example: Creating a Grid

The following code creates a simple 2×2 grid with two rows and two columns, then places a button in each cell.

// Initialize
var grid = new Grid();
// Grid fills its parent by default
grid.AddToRoot();

// Three columns showing the three main sizing types
grid.ColumnDefinitions.Add(new ColumnDefinition(new GridLength(1, GridUnitType.Star)));
grid.ColumnDefinitions.Add(new ColumnDefinition(new GridLength(2, GridUnitType.Star)));
grid.ColumnDefinitions.Add(new ColumnDefinition(GridLength.Auto));

// Two rows with different proportions
grid.RowDefinitions.Add(new RowDefinition(new GridLength(2, GridUnitType.Star)));
grid.RowDefinitions.Add(new RowDefinition(new GridLength(1, GridUnitType.Star)));

// Colors for each column — makes proportions immediately visible
Color[] columnColors = [
    new Color(180, 100, 100), // red-ish
      new Color(100, 150, 180), // blue-ish
      new Color(100, 170, 120), // green-ish
  ];
string[] columnLabels = ["1*", "2*", "Auto"];
string[] rowLabels = ["2*", "1*"];

for (int row = 0; row < 2; row++)
{
    for (int col = 0; col < 3; col++)
    {
        var background = new ColoredRectangleRuntime();

        float brightness = row == 0 ? 1.0f : 0.6f;
        var cellColor = new Color(
            (int)(columnColors[col].R * brightness),
            (int)(columnColors[col].G * brightness),
            (int)(columnColors[col].B * brightness)
        );

        background.Color = cellColor;
        background.Dock(Dock.Fill);
        grid.AddChild(background, row: row, column: col);

        var label = new Label();
        label.Text = $"Col {columnLabels[col]}\nRow {rowLabels[row]}";
        label.XUnits = GeneralUnitType.PixelsFromMiddle;
        label.YUnits = GeneralUnitType.PixelsFromMiddle;
        label.X = 0;
        label.Y = 0;
        label.XOrigin = HorizontalAlignment.Center;
        label.YOrigin = VerticalAlignment.Center;
        grid.AddChild(label, row: row, column: col);
    }
}

XnaFiddle.NET sample coming soon...

Grid displaying rows and columns

Row and Column Sizing

Each RowDefinition has a Height property and each ColumnDefinition has a Width property. Both are of type GridLength, which supports three sizing modes controlled by GridUnitType:

Star (Proportional)

Star is the default. Each row or column receives a proportion of the available space based on its value relative to the total star weight. A 1-star column and a 2-star column in a 300px grid produce a 100px column and a 200px column.

// Initialize
grid.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star) });
grid.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(2, GridUnitType.Star) });

The default ColumnDefinition and RowDefinition constructors produce a 1-star size, so new ColumnDefinition() and new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star) } are equivalent.

Absolute

Absolute sets a fixed pixel size regardless of the available space.

// Initialize
grid.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(120) });
grid.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star) });

The code above creates a fixed 120px left column and a right column that fills the remaining space.

Auto

Auto sizes a column to the widest content in that column, or sizes a row to the tallest content in that row. All cells in an Auto column are unified to the same width.

// Initialize
grid.ColumnDefinitions.Add(new ColumnDefinition { Width = GridLength.Auto });
grid.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star) });

Add Image Here

Adding Children

AddChild places a child element at a specific row and column. Row and column indices are zero-based.

// Initialize
grid.AddChild(child, row: 0, column: 1);

Calling AddChild a second time on the same child moves it to the new position — the child appears in only one cell at a time.

If the row or column index exceeds the number of defined rows or columns, it is clamped to the last valid index. This matches WPF behavior.

// Initialize
// Grid has 2 rows (indices 0 and 1). A row of 10 is clamped to row 1.
grid.AddChild(child, row: 10, column: 0);

Removing Children

Call RemoveChild to remove a child from the grid entirely.

// Initialize
grid.RemoveChild(child);

Supported Ways to Add Children

Grid requires that every child be placed in a specific cell. Only the following patterns work correctly.

Adding a FrameworkElement (Button, Panel, etc.):

// Initialize
grid.AddChild(button, row: 0, column: 1);

Adding a raw GraphicalUiElement:

// Initialize
grid.AddChild(gue, row: 0, column: 1);

The following patterns bypass the Grid's cell placement system and must not be used.

Calling AddChild without a row and column throws a NotSupportedException at runtime:

// Initialize
// This throws NotSupportedException — always supply row and column.
grid.AddChild(child);

Directly manipulating the visual tree silently produces broken layout because the Grid never records a cell assignment for the child:

// Initialize
// Do not do this.
grid.Visual.Children.Add(child.Visual);

// Do not do this either.
child.Visual.Parent = grid.Visual;

Constraining Column and Row Sizes

ColumnDefinition exposes MinWidth and MaxWidth properties, and RowDefinition exposes MinHeight and MaxHeight properties. These constraints apply to all three sizing modes (Absolute, Auto, and Star) and are specified in pixels.

// Initialize
// Column is 200px but capped at 150px
grid.ColumnDefinitions.Add(new ColumnDefinition
{
    Width = new GridLength(200),
    MaxWidth = 150
});

// Column is Auto but won't shrink below 80px
grid.ColumnDefinitions.Add(new ColumnDefinition
{
    Width = GridLength.Auto,
    MinWidth = 80
});

// Star column that won't grow beyond 300px
grid.ColumnDefinitions.Add(new ColumnDefinition
{
    Width = new GridLength(1, GridUnitType.Star),
    MaxWidth = 300
});

// Row is 50px but won't shrink below 30px
grid.RowDefinitions.Add(new RowDefinition
{
    Height = new GridLength(50),
    MinHeight = 30
});

// Star row that won't shrink below 40px
grid.RowDefinitions.Add(new RowDefinition
{
    Height = new GridLength(1, GridUnitType.Star),
    MinHeight = 40
});

MinWidth defaults to 0 (no minimum) and MaxWidth defaults to no maximum. The same defaults apply to MinHeight and MaxHeight.