C＃对象引用未设置为对象的实例。

Question

I have the following piece of code that is suppose to extract some info from a file.

private string[][] users;
private string userID;

public void getInfo()
{

    string[] lines = System.IO.File.ReadAllLines(@"U:\Final Projects\Bank\ATM\db.txt");

    for (int i = 0; i < lines.Count(); i++ )
    {
        string[] values = lines[i].Split(',');
        for (int b = 0; b < 5; b++ )
        {

            users[i][b] = values[b];

        }


    }
}

the line users[i][b] = values[b]; returns the error : " Object reference not set to an instance of an object. " but I am not sure why. the code is suppose to read each line and split the line by , and create 2 dimensional array from the info.

Answer 1

我认为你需要为数组分配空间

string[,] users = new string[M,N];

Answer 2

Unless there's code you've not shown us, you never actually created the array. Therefore, users will be null , so attempt to dereference it doesn't make sense. Hence, the exception.

Answer 3

You need to allocate users :

string[][] users = new string[n][];
for(int i = 0; i < n; i++)
{
    users[i] = new string[m];
}

n and m can be variables.