How can you set Height="*" and Height="Auto" in code behind?
For setting Height = "Auto" on most controls, you want to assign the value with double.NaN.
Example:
element.Height = double.NaN;
Setting Width/Height = "*" ( is a slightly different matter, since it only applies to a select few elements (ColumnDefinition and RowDefinition for example). The type of the Width/Height value is GridLength, rather than double.
Example (more are given on this MSDN page:
column1.Width = new GridLength(1, GridUnitType.Auto); // Auto
column2.Width = new GridLength(1, GridUnitType.Star); // *
来源：https://stackoverflow.com/questions/1497921/how-to-say-xaml-button-height-auto-in-code-behind