Question

我收到将Int转换为Double的错误，我的下一行Average[y] = Average[y] + Students[i].Marks;也无效。那么如何将int[]转换为double[]？

public static double[] Averages(StudentMarks[] Students, int amount, string[] DifferentGroups, int GroupAmount, out double[] Average)
    {
        Average = new double[Max];
        int y = 0;
        int CountGroups = 0;
        //int sum = 0;
        for (int i = 0; i < amount; i++)
        {
            if (Students[i].Group == DifferentGroups[y])
            {
                Convert.ToDouble(Students[i].Marks);
                //Average[y] = Average[y] + Students[i].Marks;
            }
        }
        return Average;
    }

主要：

 static void Main(string[] args)
    {
        int amount;
        StudentMarks[] Students;
        string[] DifferentGroups;
        int GroupAmount;
        double[] Average;
        ReadData(out Students, out amount);
        DifferentGroups = FindDifferentGroups(Students, amount, out DifferentGroups, out GroupAmount);
        Average = Averages(Students, amount, DifferentGroups, GroupAmount, out Average);

类别：

        public const int Max = 50;
    public string Surname { get; set; }
    public string Name { get; set; }
    public string Group { get; set; }
    public int AmountOfMarks { get; set; }
    public int[] Marks { get; set; }

所以学生[i] .Marks是Array。

Answer 1

Convert.ToDouble 返回一个double - 它不会使整数属性或变量成为double。

我想你想要：

        if (Students[i].Group == DifferentGroups[y])
        {
            double mark = Convert.ToDouble(Students[i].Marks);
            Average[y] = Average[y] + mark;
        }

或只是：

        if (Students[i].Group == DifferentGroups[y])
        {
            Average[y] = Average[y] + Convert.ToDouble(Students[i].Marks);
        }

Answer 2

所有Convert.ToXXX个函数返回新值。因此，您应该期望并将返回值分配给局部变量。

类似的东西：

double YourMark = Convert.ToDouble(Students[i].Marks);

Answer 3

那么如何将int []转换为double []？

通过编程。你编写代码来做到这一点。

var d = new double[Students[i].Marks.Length];
for (int j = 0; j < Students[i].Marks.Length; ++j)
{
    d[j] = Convert.ToDouble(Students[i].Marks[j]);
}

或者使用LINQ：

var d = Students[i].Marks.Select(n => Convert.ToDouble(n)).ToArray();

下次方法调用无法按照您希望的方式编译或不能正常工作时，首先要检查the documentation。

C＃无法将Int转换为Double

3 个答案: