array error in for loop on user input

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C#

private void button1_Click(object sender, EventArgs e)
        {
           BuildList(new object[] {1,tests,3});
        }



public string BuildList(object[] input)
            {
 string result = null;
            for (int i = 0; i &amp;lt; input.Length; i++)
            {
              if (input[i] != null)
                {

                   result = result + input[i].ToString() +  ",";
                }


                else
                {
                    result = "error";
                }
            }




            return result;
}

Posted 20-Jan-13 0:25am

mrDivan

Updated 20-Jan-13 1:42am

v5

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Sandeep Mewara 20-Jan-13 6:52am

And did you try it by yourself? Where are you stuck? Whats confusing you?

Sounds like a homework assignment...

mrDivan 20-Jan-13 6:57am

Hi THANK YOU FOR YOUR HELP yes i tried it works but doesn whant to give me an error when input[i]= test it should then show error only when input[i]= test and not 1or 2or3

mrDivan 20-Jan-13 7:12am

Can anyone help me

1 solution

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OriginalGriff · Accepted Answer · 2013-01-20T01:10:00

If you want to check for valid numbewrs, then you are probably best off doing a trial conversion to the actual datatype you are expecting.
So if you are expecting integer values in string form then use the int.TryParse method:

C#

public string BuildList(object[] input)
    {
    StringBuilder result = new StringBuilder();
    foreach (object o in input)
        {
        string s = o as string;
        if (s != null)
            {
            int i;
            if (int.TryParse(s, out i))
                {
                result.AppendFormat("{0}, ", s);
                continue;
                }
            }
        return "Error";
        }
    return result.ToString();
    }

Note that I have changed your code quite a bit - some of it to make your code compile (adding the return at the end), some to make it clearer (changing the for loop to a foreach) and some to make it more efficient (using a StringBuilder rather than concatenating strings). I also sorted out the indentation for you, so it is easier to read...

"hallo originalGriff thank you so much for your response the question is I have to handle the nullreference exception an the error input example"test" I do not know the type of the input"

Try this:

C#

public string BuildList(object[] input)
    {
    StringBuilder result = new StringBuilder();
    foreach (object o in input)
        {
        if (o != null)
            {
            string s = o.ToString();
            if (s != null)
                {
                int i;
                if (int.TryParse(s, out i))
                    {
                    result.AppendFormat("{0}, ", s);
                    continue;
                    }
                }
            }
        return "Error";
        }
    return result.ToString();
    }