A ColumnDefinitionCollection for the Grid instance.
ColumnDefinitions is an ordered set of ColumnDefinition objects that determine the width of each column. Each successive ColumnDefintion controls the width of each successive column. If ColumnDefinitions is empty, or if there are more columns than definitions, then columns for which there is no definition are rendered as if they were controlled by a ColumnDefinition object that has its ColumnDefinition.Width property set to GridLength.Auto.
The Grid.ColumnDefinitions property has XAML syntax support. The syntax for this operation is shown below.