You can use the CanGrow and CanShrink properties to control the appearance of report sections and fields.

For example, if you set both properties to true, a section or field automatically adjusts vertically to print or preview all the data it contains.

Sections grow and shrink vertically across their entire width.

When a section grows or shrinks, its Height property does not change. To retrieve the actual rendering height, use the RenderHeight property.

You can make fields grow or shrink to match the size of the section by setting their Field.Anchor property.

Reference

Section Class
Section Members