.NET Framework 4.6 and 4.5
Retrieves the line number from the specified character position within the text of the control. This method is not supported by MaskedTextBox.
virtual int GetLineFromCharIndex(
The GetLineFromCharIndex method is inherited from the base TextBoxBase class. However, because the MaskedTextBox control does not support multiline configuration, this method is not supported.
Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0
.NET Framework Client Profile
Supported in: 4, 3.5 SP1