public CanvasLineSpacingMode LineSpacingMode { get; set; }

Property Value

If this property is set to Default:

• Leaving LineSpacing at is default value of -1 will keep the default line spacing.
• Set LineSpacing to any positive quantity to have it affect the line spacing. And, LineSpacing and LineSpacingBaseline are absolute quantities.

If this property is set to Uniform, then the magnitude of the LineSpacing field will affect line spacing. LineSpacing and LineSpacingBaseline are absolute quantities in DIPs.

If this property is set to Proportional, then the magnitude of the LineSpacing field will affect line spacing. LineSpacing and LineSpacingBaseline are amounts by which to scale the default line spacing and line spacing baseline, respectively.

For example, to create a text format for double-spaced text, use

CanvasTextFormat textFormat = new CanvasTextFormat()
{
    LineSpacingMode = CanvasLineSpacingMode.Proportional,
    LineSpacing = 2
};

Reference