Question

我遇到C＃问题，需要帮助。

我创建了一个包含IP地址和端口对的文本文件;每行一对。它的结构是这样的：

xxx.xxx.xxx.xxx:xxxx
xxx.xxx.xxx.xxx:xxxx
xxx.xxx.xxx.xxx:xxxx

这是代码。

public void Filter()
        {
            // Read proxy from text file

            string ppath = @"C:\Program Files\HTE\IP.txt";
            StreamReader sr = new StreamReader(ppath);

            /* 
            Proxies in the text file have a contruction like this: xxx.xxx.xxx.xxx:xxxx
            It includes more than 11k proxies
            Now start to collect ip
            */

            for (int i = 0; i < 11000; i++)
            {
                if (i > 0)
                {
                    // Create a loop to ignore the line(s) which has been filter

                    for (int j = 0; j < i; j++)
                    {
                        // When j = 0, that mean it has an ignore line

                        sr.ReadLine();
                        GC.Collect();
                    }

                    // Read new line

                    string str_2 = sr.ReadLine();
                    int position_2 = str_2.IndexOf(":");

                    // Get ip

                    string str_ip_2 = str_2.Substring(0, position_2);
                    int tail_2 = str_2.Length - position_2;
                    string str_tmp_2 = str_2.Substring(position_2, tail_2);
                    int subtraction_2 = str_tmp_2.Length - 1;

                    // Get port

                    string str_port_2 = str_tmp_2.Substring(1, subtraction_2);
                    GC.Collect();
                }
                else if (i == 0)
                {
                    string str = sr.ReadLine();

                    // find ":" in the postion of the first line

                    int position = str.IndexOf(":");

                    // Get ip

                    string str_ip = str.Substring(0, position);

                    // The tail of string in line is proxy port

                    int tail = str.Length - position;
                    string str_tmp = str.Substring(position, tail);
                    int subtraction = str_tmp.Length - 1;

                    // Get port

                    string str_port = str_tmp.Substring(1, subtraction);
                    GC.Collect();
                }
            }

错误代码：

string str_2 = sr.ReadLine();
int position_2 = str_2.IndexOf(":");

我尝试了很多方法，但我无法修复它。

提前致谢。

Answer 1

您对sr.ReadLine()的调用最有可能返回null，使str_2为null，并导致str_2.IndexOf抛出异常。

您有2次致电.ReadLine()。你实际阅读了多少行数据？如果只有一行，则第二次调用将返回null，从而导致上述行。

如何修复此错误：nullreferenceexception未处理

1 个答案: