Empty String to Double C#

问题

At this moment i am trying to get a double value from textbox like this:

String.IsNullOrEmpty(textBox1.Text) ? 0.0 : Double.Parse(textBox1.Text)

But there is a problem, i cant get how to parse empty textbox?

For example if to try this code with OleDb and Excel with empty textbox, we will get error

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

回答1:

double val;
if(!double.TryParse(textBox.Text,out val))
    val = 0.0

回答2:

Did you try Double.TryParse(String, NumberStyles, IFormatProvider, Double%)?

This could help to solve problems with various number formats.

回答3:

If Double.TryParse is unable to parse the string, it returns false and sets the out parameter to 0.

double d;
if(double.TryParse(textBox1.Text, out d)
{
  // valid number
}
else
{
  // not a valid number and d = 0;
}

Or

double d;
double.TryParse(textBox1.Text, out d)
// do something with d.  

Also note that you can use the out parameter in additional logic within the same if statement:

double d;
if(double.TryParse(textBox1.Text, out d) && d > 500 && d < 1000)
{
  // valid number and the number is between 501 and 9999
}

回答4:

double result;
Double.TryParse("",out result);

If TryParse is true, the result will have a double value Further you can use if condition,

result = Double.TryParse("",out result) ? result : 0.00

回答5:

Why don't you just use Double.TryParse that doesn't throw exception?

来源：https://stackoverflow.com/questions/12583371/empty-string-to-double-c-sharp