C＃WinForms-如何使用2个值之间的几个文本框（执行操作）

Question

I have a form, where a 'user' inputs values into several textboxes and if the values are between certain ranges I want it to do something.

Is it possible to check multiple textboxes simultaneously as opposed to having them checked like so:

if (int.Parse(textbox1.Text) >= 100 && int.Parse(textbox1.Text) <= 2000)
{
    mylist.Add(int.parse(textbox1.text));
}
if (int.Parse(textbox2.Text) >= 100 && int.Parse(textbox2.Text) <= 2000)
{
    mylist.Add(int.parse(textbox1.text));
}
if (int.Parse(textbox3.Text) >= 100 && int.Parse(textbox3.Text) <= 2000)
{
    mylist.Add(int.parse(textbox3.text));
}

Answer 1

One possibility would be to put them in a list:

var textboxes = new List<TextBox>(new[] { textbox1, textbox2, textbox3 });

and then loop through this list and probably parse the value only once:

foreach (var t in textboxes) 
{
    int value = int.Parse(t.Text);
    if (value >= 100 && value <= 2000)
    {
        mylist.Add(value);
    }
}

or if you prefer using LINQ you could also do this one liner:

IList<int> mylist = textboxes
    .Select(t => int.Parse(t.Value))
    .Where(value => value >= 100 && value <= 2000)
    .ToList();

Answer 2

Extract method:

public void AddValue(string text, List<int> list)
{
    var value = int.Parse(test);
    if (value >= 100 && value <= 2000)
    {
        list.Add(value);
    }
}

And call it:

var list = new List<int>();
AddValue(textbox1.Text, list);
AddValue(textbox2.Text, list);
AddValue(textbox3.Text, list);

Answer 3

You could write a simple boolean method that does this work on a textbox passed to it and tells the calling code if the parsing is successful

private bool ParseText(TextBox txt, List<int> theList)
{
    int value;
    if(Int32.TryParse(txt.Text, out value))
    {
        if(value >= 100 && value <= 2000)
        {
            theList.Add(value);
            return true;
        }
     }
    return false;
} 

Now you could call this method

if(!ParseText(textBox1, mylist))
    MessageBox.Show("Invalid value in TextBox1");
if(!ParseText(textBox2, mylist))
    MessageBox.Show("Invalid value in TextBox2");
if(!ParseText(textBox3, mylist))
    MessageBox.Show("Invalid value in TextBox3");

Notice that a textbox whose text is expected to be an integer but is typed by the user should be always parsed using Int32.TryParse instead of Parse because Parse raises an exception if the text cannot be converted to an integer