Dictionary with a Point!!

Question

Hi all I hope someone can help me out!! I'm fairly new to C#. I've established a dictionary: Dictionary string  Point > addPositionDict = new Dictionary string  Point >(); I initialized the dictionary: Point addPoint = new Point (); addPoint.X = 0; addPoint.Y = 0; and added my points with their given names: addPositionDict.Add(name_Out addPoint); Now knowing their names I want to update their positions and I tried like so: addPositionDict[nameOut].X = x_matrix; However there is an error which I can't understand: Cannot modify the return value of 'System.Collections.Generic.Dictionary .this[string]' because it is not a variable What am I doing wrong? what exactly is not a variable? Again Take it easy on the language jargon -- I'm fairly new to C#.

Vulpes · Answer

The problem is that Point is a struct (i.e. a value type) rather than a class. Consequently addPositionDict[name_Out].X is a value rather than a variable and you can't assign anything to a value. The workaround is to do it like this: addPositionDict[name_Out] = new Point(x_matrix addPositionDict[name_Out].Y); Notice that here addPositionDict[name_Out].Y is simply being used as a value - we're not trying to assign anything to it. If Point had been a class (i.e. a reference type) rather than a struct then your original code would have worked because addPositionDict[name_Out].X would then have been regarded as a variable.

Marty Habicht · Answer

Tahak you so much for this! For once nobody is speaking in # jargon. Easy to understand. Wow!!