从xaml中的文本框中获取价值

Question

private void search(object sender, RoutedEventArgs e)
{
    if (number.Text < 455)
    {
        string site;
        site = number.Text;
        var rs = Application.GetResourceStream(new Uri("def/f" + site + ".html", UriKind.Relative));
        StreamReader sr = new StreamReader(rs.Stream);
        browser.NavigateToString(sr.ReadToEnd());
    }
    else
    {
        MessageBox.Show("Enter Value between 1 to 454");
    }
} 

I gave InputScope="Number" in TextBox. So the user cant type words. gave I have created the button with name, so if button pressed search function will be called. I need to validate that the user entered text in between 1 to 454. If it is, it should go on. Other wise i should alert them like i do above. But it shows error like,

Error 1 Operator '<' cannot be applied to operands of type 'string' and 'int'

Answer 1

You are comparing Text which is string with integer which is 455 . Before comparison convert the text to integer and do this.

if (Convert.ToInt32(number.Text) < 455)

Here is your solution

int num = 0;

if (int.TryParse(number.Text, out num) && num > 0 && num < 455)
{
    string site;
    site = number.Text;
    var rs = Application.GetResourceStream(new Uri("def/f" + site + ".html", UriKind.Relative));
    StreamReader sr = new StreamReader(rs.Stream);
    browser.NavigateToString(sr.ReadToEnd());
}
else
{
    MessageBox.Show("Enter Value between 1 to 454");
}

Answer 2

Well, the message should tell you what is wrong. Text is a string and you are using it as an int .

private void search(object sender, RoutedEventArgs e)
{
    int n;
    if(int.TryParse(number.Text, out n))
    {
       if (n < 455)
       {
           var rs = Application.GetResourceStream(new Uri("def/f" + number.Text + ".html", UriKind.Relative));
           StreamReader sr = new StreamReader(rs.Stream);
           browser.NavigateToString(sr.ReadToEnd());
       }
       else
       {
           MessageBox.Show("Enter Value between 1 to 454");
       }
    }
} 

Answer 3

You can't guarantee that the user will type a valid number, so this is one way to check:

int parsed;

if (int.TryParse(number.Text, out parsed) && parsed < 455)
{
    // Logic to execute when valid
}
else
{
    MessageBox.Show("Enter Value between 1 to 454");
} 

Answer 4

You should use either Convert.ToInt32() or int.TryParse() to convert your string to an integer in order to do the comparison. You can't directly compare strings and integers the way you're doing it.

Answer 5

Common C# question

int iNumber = -1;
if(int.TryParse(textBoxNumber.Text, out iNumber))
{
 // iNumber now have value you can check
 // ...
}
else { } // failed to parse string

Answer 6

It should be something like this probably: we should check (num > 0 && num < 455). We should check -ve values as well.

int num = -1

if(int.TryParse(number.Text, out num))
    {
       if (num > 0 && num < 455)
       {
         //Do here 
       }
       else
       {
           MessageBox.Show("Enter Value between 1 to 454");
       }
    }