Check for a double variable

Question

I need to check if I have a data type variable double. This is what I tried:

try
{
    double price = Convert.ToDouble(txtPrice.Text);
}
catch (FormatException)
{
    MessageBox.Show("Product price is not a valid price", "Product price error", MessageBoxButtons.OK, MessageBoxIcon.Error);
    return false;
}

I thought this would work, but obviously I didn’t understand if txtPrice.Textthere was anything other than the number in it, the class Convertwould just parse it.

How can I confidently check if a variable is double?

Answer 1

Use this:

double price;
bool isDouble = Double.TryParse(txtPrice.Text, out price);
if(isDouble) {
  // double here
}

Answer 2

How can I confidently check if a variable is double?

You need to be clearer about what you are really trying to do here. I don’t think you are asking what you think, what you are asking, and it is worth knowing about the differences in terminology.

, double, a double. , object, ValueType ,

if (value is double)

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, IFormatProvider . , .

, :

double result;
// For suitable values of text, style and culture...
bool valid = double.TryParse(text, style, culture, out result);

valid, , . valid , result . valid , result 0.

Answer 3

Double.TryParse:

double price;
if (Double.TryParse(txtPrice.Text, out price))
{
    Console.WriteLine(price);
}
else
{
    Console.WriteLine("Not a double!");
}

Answer 4

- -

  double doubleVar;
    if( typeof(doubleVar) == double ) {
        printf("doubleVar is of type double!");
    }

, double.

Answer 5

.GetType(), , , , . . http://msdn.microsoft.com/en-us/library/58918ffs(v=vs.71).aspx .

Answer 6

• double.ParseExact
• Regex, , .

Answer 7

Double.TryParse - , .

Answer 8

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string Str = textBox1.Text.Trim();
double Num;
bool isNum = double.TryParse(Str, out Num);
if (isNum)
MessageBox.Show(Num.ToString());
else
MessageBox.Show("Invalid number");

Answer 9

double.TryParse(), false, .

Answer 10

:

double.Parse(txtPrice.Text);

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