int.Parse，输入字符串的格式不正确

Question

How would I parse an empty string? int.Parse(Textbox1.text) gives me an error:

Input string was not in a correct format.
System.FormatException: Input string was not in a correct format.

If the text is empty ( Textbox1.text = '' ), it throws this error. I understand this error but not sure how to correct this.

Answer 1

If you're looking to default to 0 on an empty textbox (and throw an exception on poorly formatted input):

int i = string.IsNullOrEmpty(Textbox1.Text) ? 0 : int.Parse(Textbox1.Text);

If you're looking to default to 0 with any poorly formatted input:

int i;
if (!int.TryParse(Textbox1.Text, out i)) i = 0;

Answer 2

Well, what do you want the result to be? If you just want to validate input, use int.TryParse instead:

int result;

if (int.TryParse(Textbox1.Text, out result)) {
    // Valid input, do something with it.
} else {
    // Not a number, do something else with it.
}

Answer 3

if(!String.IsNullOrEmpty(Textbox1.text))
    var number = int.Parse(Textbox1.text);

Or even better:

int number;

int.TryParse(Textbox1.Text, out number);

Answer 4

Try this:

int number;
if (int.TryParse(TextBox1.Text, out number))
{
    //Some action if input string is correct
}

Answer 5

If the input is a number or an empty string this will work. It will return zero if the string is empty or else it will return the actual number.

int.Parse("0"+Textbox1.Text)

Answer 6

You could also use an extension method like this:

public static int? ToNullableInt32(this string s)
{
    int i;
    if (Int32.TryParse(s, out i)) return i;
    return null;
}

Here's the reference: How to parse a string into a nullable int in C# (.NET 3.5)

Answer 7

你可以用简单的try/catch包装它......