How can I convert String to Int?

Question

I have a TextBoxD1.Text and I want to convert it to an int to store it in a database.

How can I do this?

Answer 1

Be careful when using Convert.ToInt32() on a char! It will return the UTF-16 code of the character!

If you access the string only in a certain position using the [i] indexing operator, it will return a char and not a string!

String input = "123678";
                    ^
                    |
int indexOfSeven =  4;

int x = Convert.ToInt32(input[indexOfSeven]);             // Returns 55

int x = Convert.ToInt32(input[indexOfSeven].toString());  // Returns 7

Answer 2

In C# v.7 you could use an inline out parameter, without an additional variable declaration:

int.TryParse(TextBoxD1.Text, out int x);

Answer 3

int.TryParse()

It won't throw if the text is not numeric.

Answer 4

int x = Int32.TryParse(TextBoxD1.Text, out x) ? x : 0;

Answer 5

You can write your own extension method

public static class IntegerExtensions
{
    public static int ParseInt(this string value, int defaultValue = 0)
    {
        int parsedValue;
        if (int.TryParse(value, out parsedValue))
        {
            return parsedValue;
        }

        return defaultValue;
    }

    public static int? ParseNullableInt(this string value)
    {
        if (string.IsNullOrEmpty(value))
        {
            return null;
        }

        return value.ParseInt();
    }
}

And wherever in code just call

int myNumber = someString.ParseInt(); // Returns value or 0
int age = someString.ParseInt(18); // With default value 18
int? userId = someString.ParseNullableInt(); // Returns value or null

In this concrete case

int yourValue = TextBoxD1.Text.ParseInt();

Answer 6

You can try the following. It will work:

int x = Convert.ToInt32(TextBoxD1.Text);

The string value in the variable TextBoxD1.Text will be converted into Int32 and will be stored in x.