“FormatException is unhandled”，程序不计算结果

我目前正在学习C#，我有点卡在作业上。我正在使用Visual Studio 2010，我的任务如下：

编写一个程序，创建一个由教授 ID 和三个评级组成的教授评级类。这三个评级用于评估易用性、有用性和清晰度。在单独的实现类中，允许用户输入值。调用构造函数以创建 ProfessorRating 类的实例。包括适当的属性。不允许在构造对象后更改 ID。在 ProfessorRating 类中提供一个方法来计算和返回总体平均评分。打印实现类中小数点右侧没有数字的所有评级和平均评级格式。使用单个类方法输入所有数据。

到目前为止，我已经完成了大部分作业，但是我最终遇到了两个我自己无法弄清楚的错误。

代码在两个文件中，这是第一个：

//ProfessorApplication.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Lesson4_v4
{
class ProfessorApplication
{
    static void Main( )
    {
        ProfessorRating professorObject = new ProfessorRating();
        int pID;
        int cR;
        int hR;
        int eR;
        DisplayInstructions(); //Show instructions
        pID = DataEntry("Professor ID of the professor you'd like to rate");
        cR = DataEntry("clarity rating of the professor");
        hR = DataEntry("helpfulness rating of the professor");
        eR = DataEntry("easiness rating of the professor");
        professorObject.GradeAverage();
        Console.Clear();
        Console.Write(professorObject);
        Console.ReadLine();
    }
    static void DisplayInstructions()
    {
        Console.Beep();
        Console.WriteLine("Hello! This program will allow you to calculate a Professor's rating based on three categories!");
        Console.WriteLine(" ");
        Console.WriteLine("You will be asked for the the professor ID and a grade of 1-10.");
        Console.WriteLine(" ");
        Console.WriteLine("Please refer to the scale below.");
        Console.WriteLine(" ");
        Console.WriteLine("  0    1    2    3    4    5    6    7   8    9    10 ");
        Console.WriteLine("Worst                                             Best");
        Console.Read();
    }
    static int DataEntry(string rating1)
    {
        string inputValue;
        int Rating;
        Console.WriteLine("Please enter the {0}: ",rating1);
        inputValue = Console.ReadLine();
        Rating = int.Parse(inputValue); //System.FormatException was unhandled according to VS2010
    }
}
}

下面是第二个文件中的代码：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Lesson4_v4
{
    class ProfessorRating
    {
    private int professorID; // Professor ID
    int helpRating; // Helpfulness Rating
    int cleaRating; // Clarity Rating
    int easyRating; // Easiness Rating
    public ProfessorRating() //default constructor           
    {
    }
    public ProfessorRating(int pID) //1 parameter constructor
    {
        professorID = pID;
    }
    public ProfessorRating(int pID, int hR, int cR, int eR) //all parameter constructor
    {
        professorID = pID;
        helpRating = hR;
        cleaRating = cR;
        easyRating = eR;
    }
    public int GradeAverage() //is supposed to calculate the average, but shows as "0"
    {
        return (helpRating + cleaRating + easyRating) / 3;
    }
    public override string ToString()
    {
        return "The average is " + GradeAverage();
    }
}
}

感谢您的帮助！

    int pID;
    int cR;
    int hR;
    int eR;

    double pID;
    double cR;
    double hR;
    double eR;

static int DataEntry(string rating1)
{
    string inputValue;
    int Rating;
    Console.WriteLine("Please enter the {0}: ",rating1);
    inputValue = Console.ReadLine();
    Rating = int.Parse(inputValue); //System.FormatException was unhandled according to VS2010
}

    static int DataEntry(string rating1)
    {
        string inputValue;
        int Rating;
        Console.WriteLine("Please enter the {0}: ",rating1);
        inputValue = Console.ReadLine();
        Rating = int.Parse(inputValue); //System.FormatException was unhandled according to VS2010
Return Rating;
    }

static void Main( )
{
    ProfessorRating professorObject = new ProfessorRating();
    int pID;
    int cR;
    int hR;
    int eR;

pID = DataEntry("Enter the ID of the Professor you would like to rate");
        cR = DataEntry("Please rate the clearity of the information provided");
        hR = DataEntry("Please rate your instructor on their helpfulness");
        eR = DataEntry("Please rate your material on its easiness");
        ProfessorRating professorObject = new ProfessorRating(pID, cR, hR, eR);
        professorObject.GradeAverage();