NullReference Exception in converting string to Char array

Question

It is showing Null Reference Exception on line char[] myChar = read.ToCharArray();.

I am unable to figure out. Please help

class Program
{
    static void Main(string[] args)
    {
        StreamReader myReader = new StreamReader("TextFile1.txt");
        string read = "";

        while (read != null)
        {
            read = myReader.ReadLine();
            Console.WriteLine(read);

        }

       char[] myChar = read.ToCharArray();

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

        Console.WriteLine(read);
        myReader.Close();
        Console.ReadKey();
    }
}

Your while loop right above that is exiting only after read is null, so of course read.ToCharArray() will give the exception. — DocMax
– DocMax, Commented Sep 7, 2013 at 17:23
at that line, read will be null, because of the condition in the while loop. — Нет войне
– Нет войне, Commented Sep 7, 2013 at 17:24
Maybe you could tell us what you want the code from read.ToCharArray() to achieve? — Нет войне
– Нет войне, Commented Sep 7, 2013 at 17:26
I need to match my string with a regular expression and for that reason i need to convert the string into char array to match every character in the string. can you help me out with any other logic? — DevFreak
– DevFreak, Commented Sep 7, 2013 at 17:37
You should describe what each part of your program is doing. For example when does this loop end: while (read != null) For example, step 1: Read the entire file and print it out. Step 2 I want to access the file again; I'll have to restart at the beginning of the file. — dcaswell
– dcaswell, Commented Sep 7, 2013 at 18:06

Adil · Accepted Answer · 2013-09-08 02:04:08Z

1

The read should be null when the loop is finished and calling ToCharArray on null should give exception. you can put this statement in while loop. I believe you are trying to do some experimentation as you have already printed the string with Console.WriteLine(read);

while ((read = sr.ReadLine()) != null)
{      
    Console.WriteLine(read);
    char[] myChar = read.ToCharArray();
    for (int i = 0; i < myChar.Length; i++)        
        Console.WriteLine(myChar[i]);       
}

edited Sep 8, 2013 at 2:04

answered Sep 7, 2013 at 17:24

Adil

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Comments

Gonzix · Accepted Answer · 2013-09-07 18:08:36Z

0

        StringBuilder sb = new StringBuilder();
        using (StreamReader sr = new StreamReader("TestFile.txt")) 
        {
            string line;
            // Read and display lines from the file until the end of 
            // the file is reached.
            while ((line = sr.ReadLine()) != null) 
            {
                Console.WriteLine(line);
                sb.Append(line);
            }
        }

        var chars = sb.ToString().ToCharArray();

However, you should add each line into a stringbuilder and then convert it into char array. The thing is what you really want to do?

edited Sep 7, 2013 at 18:08

answered Sep 7, 2013 at 17:59

Gonzix

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