using System;

using System.Collections.Generic;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var inputString = "32:432;2:45;34:64;";

        string[] jointProbability = inputString.Split(new[] { ';' }, StringSplitOptions.RemoveEmptyEntries);

        Dictionary<string, string> jointProbabilityEntries = jointProbability.Select(item => item.Split(':')).ToDictionary(s => s[0], s => s[1]);

        foreach(var entry in jointProbabilityEntries)

        {

            Console.WriteLine(entry.Key+":"+entry.Value);

        }

    }

}