C# error basic function

Question

I have a problem with my function

public class PS3
{
    public static void restoreAllClassesNames(string A, string B, string C/*, string A1, string B1, string C1, string A2, string B2, string C2, string A3, string B3, string C3, string A4, string B4, string C4*/)
    {
        A = returnLine("a.txt", 0);
        B = returnLine("a.txt", 1);
        C = returnLine("a.txt", 2);
    }

    public static string returnLine(string fileName, int line)
    {
        StreamReader SR = new StreamReader(fileName);
        List<string> myList = new List<string>();
        string linePath;
        while ((linePath = SR.ReadLine()) != null)
            myList.Add(linePath);

        return myList[line];
    }

So, when I am do this :

Functions.PS3.restoreAllClassesNames(textBox1.Text, textBox2.Text, textBox3.Text);

My textbox1 , 2 & 3 contains nothing, yet it should work

You might want to read this article about parameter passing. — Thomas Levesque
– Thomas Levesque, Commented Aug 21, 2014 at 22:21

D Stanley · Accepted Answer · 2014-08-21 22:17:16Z

6

You are passing in the value of the Text property of each TextBox, so changing that value within the restoreAllClassesNames method does nothing to the original control.

You can either pass in the controls themselves (since they are reference types):

public static void restoreAllClassesNames(Control A, Control B, Control C)
{
    A.Text = returnLine("a.txt", 0);
    B.Text = returnLine("a.txt", 1);
    C.Text = returnLine("a.txt", 2);
}

or make the strings out parameters:

public static void restoreAllClassesNames(out string A, out string B, out string C)
{
    A = returnLine("a.txt", 0);
    B = returnLine("a.txt", 1);
    C = returnLine("a.txt", 2);
}

and assign the text to the control from the calling method:

string a;
string b;
string c;

Functions.PS3.restoreAllClassesNames(out a, out b, out c);   

textBox1.Text = a;
textBox2.Text = b;
textBox3.Text = c;

you could also return a List<string>, a Tuple<string, string, string>, etc., etc.

answered Aug 21, 2014 at 22:17

D Stanley

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1 Comment

Dai Over a year ago

Also, the code is leaking file handles because SR owns its underlying stream but isn't being closed afterwards.

Ajay · Accepted Answer · 2014-08-21 23:03:43Z

StreamReader is looking for the file in bin\Debug\ folder

You can provide the filepath

public static string returnLine(string fileName, int line)
        {
            var filepath = "D:/" + fileName; /*Your file path*/
            if (File.Exists(filepath))
            {
                StreamReader SR = new StreamReader(filepath);
                List<string> myList = new List<string>();
                string linePath;
                while ((linePath = SR.ReadLine()) != null)
                    myList.Add(linePath);
                if (myList.Count > 0)
                    return myList[line];
                else
                    return "No record found";
            }
            else
            {
                return "File not found";
            }
        }

Lamloumi Afif · Accepted Answer · 2014-08-21 22:22:14Z

-1

pass the reference of the string not its values :

  public static void restoreAllClassesNames( ref string A,  ref string B,  ref string C/*, string A1, string B1, string C1, string A2, string B2, string C2, string A3, string B3, string C3, string A4, string B4, string C4*/)
            {
                A = returnLine("a.txt", 0);
                B = returnLine("a.txt", 1);
                C = returnLine("a.txt", 2);
            }

You call your method like this

string txt1 = textBox1.Text;
string txt2 = textBox2.Text;
string txt3 = textBox3.Text;
    Functions.PS3.restoreAllClassesNames(ref txt1 , ref txt2 , ref txt3 );
textBox1.Text = txt1;
textBox2.Text = txt2;
textBox3.Text = txt3;

Check this link

answered Aug 21, 2014 at 22:22

Lamloumi Afif

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4 Comments

D Stanley Over a year ago

You can't pass a property by reference.

Thomas Levesque Over a year ago

No need to initialize txt1, txt2 and txt2; just make the parameters out instead of ref

Lamloumi Afif Over a year ago

@ThomasLevesque : You can use ref or out in this case ( twice can solve the problem) , there is no difference( for me) except the initialization

Thomas Levesque Over a year ago

@LamloumiAfif, yes, but using ref is misleading for the caller, since it implies that the method will use the initial value of the parameter.

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