String to numeric conversion in c#

Question

I am trying to write a function to convert the contents of a string "12345" to an int.

If the string is blank i would like to return null (uninitialized), not the value 0.

Problem is, functions do not return un-initialized values.

My code will not compile as Retval can return an uninitialized value......

My attempt so far:

public int ConvertStringToNumber(String TheString)
{
    // Uninitialized
    int Retval;

    if (TheString.Length > 0)
    {
        // We have a valid string
        if (Int32.TryParse(TheString, out Retval))
        {
            // We have a valid Number
        }
    }

    // Return the number or null
    return Retval;
}

Devesh · Accepted Answer · 2013-03-26 07:13:21Z

8

Can you use Nullable int ? it will allow set as nullable . See here : http://www.codeproject.com/Articles/11854/C-2-0-Nullable-Types

answered Mar 26, 2013 at 7:13

Devesh

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Comments

d.moncada · Accepted Answer · 2013-03-26 07:37:46Z

1

You can use a nullable int (more info here).

Nullable types can represent all the values of an underlying type, and an additional null value.

public int? ConvertStringToNumber(String TheString)
{
    int retval;
    bool isInt = Int32.TryParse(TheString, out retval);
    return isInt ? retval : null;
}

Note: When using nullable types, you'll need to use a cast or get it's value. See here.

Example:

int? n = ConvertStringToNumber("123");

int value = n.Value;
// or
int value = (int)n;

edited Mar 26, 2013 at 7:37

answered Mar 26, 2013 at 7:16

d.moncada

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Comments

Itachi · Accepted Answer · 2013-03-26 08:27:10Z

0

If you assigned a value to the Retval object AT THE FIRST TIME, then the value is valid in THAT area ONLY. So, Retval is null when you return it.

answered Mar 26, 2013 at 8:27

Itachi

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Comments

Navnath Godse · Accepted Answer · 2013-10-10 06:56:38Z

0

since Int32.TryParse(TheString, out Retval) require int type not nullable

public int? ConvertStringToNumber(String TheString)
{

    // Uninitialized
    int Retval;

    if (TheString.Length > 0)
    {

        // We have a valid string

        if (Int32.TryParse(TheString, out Retval))
        {

            // We have a valid Number
            return Retval;
        }

    }

            // Return the number or null

    return null;
}

edited Oct 10, 2013 at 6:56

Navnath Godse

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answered Mar 26, 2013 at 7:22

Nasir Mahmood

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Comments

Elshan · Accepted Answer · 2013-03-26 07:28:59Z

-1

Simple extension method to resolve your problem

using System;

namespace temp
{
    class Program
    {
        static void Main(string[] args)
        {
            string valu = "";
            Console.WriteLine(valu.ToInt32());
            Console.ReadLine();
        }
    }
    public static class MyExtentions
    {
        public static int ToInt32(this string s)
        {
            int x;
            if (s != null)
            {
                if (s.Length > 1)
                    x = Convert.ToInt32(s);
                else
                    x = 0;
            }
            else
            {
               x= 0;
            }
            return x;
        }
    }
}

edited Mar 26, 2013 at 7:28

answered Mar 26, 2013 at 7:22

Elshan

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Comments

XTGX · Accepted Answer · 2013-03-27 18:03:02Z

-2

int? x = ConvertStringToNumber("1");

int value = x.Value;

String to numeric conversion in c#

edited Mar 27, 2013 at 18:03

answered Mar 26, 2013 at 7:14

XTGX

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