WPF - Cannot convert text from TextBox to Double

Question

I am having trouble converting the text from a TextBox to Double. In Win Forms it was fairy simple to convert it using the ToDouble() method, however now in WPF I am having issues with this.

First of all in the Main Window I have an int declared to help Id-ing other controls, this int is incremented only when pressing a button in order to add extra controls. Also I have a double[] declared to pass information from textboxes.

This is the int and double declaration:

public partial class MainWindow : Window
    {
        int i = 0;
        double[] Fi;

Now in the button pressed method I am trying to pass the information to the array from the textbox:

Fi[i] = double.Parse(textBox15.Text);
            MessageBox.Show("" + Fi[i]);

This is the error message I get when debugging the code:

An unhandled exception of type 'System.NullReferenceException' occurred in WpfApplication2.exe

Additional information: Object reference not set to an instance of an object.

The textbox is not null since I am inputing value to it from the keyboard, in this stage i = 0. Any advise on this matter? It is the 3rd attempt to convert, I have also user so far:

Fi[i] = Convert.ToDouble(textBox15.Text);

also giving the same error.

Step through it with the debugger and see what is or isn't null. My guess? Fi. — Charles Mager, May 09 '15 at 16:23

score 0 · Answer 1 · answered May 09 '15 at 16:25

0

You have to create a new array... for example:

double[] fi = new double[10];

answered May 09 '15 at 16:25

Peter Schneider

2,578
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score 0 · Accepted Answer · answered May 09 '15 at 16:25

0

Init the Fi array first:

double [] Fi = new double [3];

And have a look at this : https://msdn.microsoft.com/en-us/library/9b9dty7d.aspx

answered May 09 '15 at 16:25

lboshuizen

2,636
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Thank you for the answer, it did the trick ! So I take it I cannot just create an array without knowing how many elements it will have ? That was what I was trying to do. – Bogdan U May 09 '15 at 16:44
Take a look at `List` – Charles Mager May 09 '15 at 16:52
Thank you Charles, I went through Lists and it was even better to use them. – Bogdan U May 10 '15 at 08:02

WPF - Cannot convert text from TextBox to Double

2 Answers2