Getting listings to highlight Func<x,x,x>

Question

Given this image:

How would you create a lstdefinelanguage that would make Func<double, double, double> highlighted without having to add spaces after each comma?

\documentclass{book}
\usepackage{listings}
\usepackage{color}
\usepackage{xcolor}
\lstdefinelanguage{CSharp}
{
      basicstyle=\ttfamily,
      keywordstyle=\color{blue!60!black}\bfseries,
      morekeywords={double,Func},
      alsoletter={[, ]},
}

\lstset{
    basicstyle=\footnotesize\ttfamily,
    language=[Sharp]C,
    alsolanguage=CSharp,      
    keywordstyle=\color[rgb]{0.0,0,1.0}\bfseries  
}
\begin{document}

\begin{lstlisting}
double x = 10;
Func<double> x = 10;
Func<double, double, double> x = 10;
Func<double , double , double> x = 20;
\end{lstlisting}

\end{document}

Answer 1

Here a simple example that shows an approach.

Based on the given information in the comments you want to highlight combinations like int[]. In this case you shouldn't use alsoletter. Instead use otherkeywords

\documentclass[varwidth,border=10,convert={png,size=800,density=1000}]{standalone}
\usepackage{xcolor}
\usepackage{bera}
\usepackage{listings}
\lstdefinelanguage{mylang}{%
  basicstyle=\ttfamily,
  keywordstyle=\color{blue!60!black}\bfseries,
 morekeywords={double,Func,int},
  sensitive=false,
 otherkeywords={[, ]}
}
\begin{document}
\begin{lstlisting}[language=mylang]
double x = 10;
Func<double> x = 10;
Func<double, double, double> x = 10;
Func<double , double , double> x = 10;
int[];
\end{lstlisting}
\end{document}