C＃添加到列表不起作用

Question

I am new to C# and I am just trying to create a simple program to perform some basic calculations on VS2010. The problem I'm having is that I don't seem to be able to add the calculated value to a list.

List<double> distance = new List<double>();
List<double> speed = new List<double>();

// distance and speed are populated using Add()

List<double> slope = new List<double>();
double rise, run;
for (int i= 0; i< distance.Count(); i++)
{
    rise = 0.0;
    run = 0.0;
    if (i> 0)
    {
        rise = speed[i] - speed[i- 1];
        run = distance[i] - distance[i- 1];

        if (rise == 0 || run == 0)
        {
            slope.Add(0.0);
        }
        else slope.Add(rise/run);

    }
    else slope.Add(0.0);
    Console.WriteLine("{0}, {1}, {2}, {3}, {4}", i, rise, run, rise/run, slope);
}

The resulting output is

...
10, -21.7, -0.089, -243.82, System.Collection.Generic.List`1[System.Double]
11, 1.49, -0.088, -16.93, System.Collection.Generic.List`1[System.Double]
12, -4.51, -0.514, 87.74, System.Collection.Generic.List`1[System.Double]

All other uses of the Add() function have been fine, however, these are all adding elements or averages of another list of the same type.

Why does the Add() not like the calculation using two double values? What should I be doing here?

Answer 1

您可以使用string.Join来创建以逗号分隔的列表

Console.WriteLine("{0}, {1}, {2}, {3}, {4}", i, rise, run, rise/run, string.Join(", ", slope));

Answer 2

Console.WriteLine("{0}, {1}, {2}, {3}, {4}", i, rise, run, rise/run, slope);

All the values you print there are regular numbers—except for slope . It is a list that contains numbers out of each iteration. Because it is a more complex type, its ToString() method just gives its exact type.

You have two choices here. Either you only print the value you just added to the list, slope[i] , or you print the whole list:

// print the value
Console.WriteLine("{0}, {1}, {2}, {3}, {4}", i, rise, run, rise/run, slope[i]);

// print the whole list
Console.WriteLine("{0}, {1}, {2}, {3}, {4}", i, rise, run, rise/run, string.Join(", ", slope));

Answer 3

Because that's not the way to show a list in the console.

Try this:

for(int i=0;i<slope.Count;i++)
{ 
    Console.WriteLine(slope[i]);
}

Answer 4

Iterate to list as follows,

foreach(double d in slope)
 Console.WriteLine(d); //or Console.Write(d+" ");

You have to do like this because, list not a valid (here valid means the way you wanted to see the output) argument for Console.WriteLine . c# will do .toString() to the list show the output, hence you see System.Collection.Generic.List1[System.Double] . You have to iterate over it.

Answer 5

The reason you are seeing the text is because your format operation is taking the ToString() method.

Your rise/run division appears to have been assigned the type System.Double rather than the primitive type double, hence ToString() is giving a different result.

There's nothing 'wrong', but you may wish to explicitly use the primitive double type for convenience in this situation.