How can I allow only one decimal point in a textbox?

问题

Here is the code in C# to allow only one decimal point in a textbox:

if textbox5.text.contains(".") && e.keychar="."
{
e.handled=true
}

I have to use it in VB.NET 2003 version, but I can't use the contains property. How can I do this?

回答1:

How about using the Text.IndexOf(".") method instead? If it returns >=0 then you already have a decimal point.

If (textbox5.Text.IndexOf(".") >= 0 And e.KeyChar = ".") Then e.Handled = True

回答2:

Don't forget about the user's locale and number formats. I believe using a period ('.') as a decimal character is in the minority, world-wide. You can use CurrentUICulture's NumberFormat field to help you parse in the most correct way. Try using:

decimal d;
bool isValidInput = decimal.TryParse(
    textBox1.Text,
    System.Globalization.NumberStyles.AllowDecimalPoint,
    System.Globalization.CultureInfo.CurrentUICulture.NumberFormat,
    out d);

This will validate whether a number was entered properly. Using other NumberStyles flags, you can control what kinds of numbers you want to allow, for example things like thousands separators.

*Sorry for C# here. VB.NET should be easy to adapt from this though; maybe some kind soul can edit it in.

回答3:

package Utility
{

    import flash.events.Event;

    import flashx.textLayout.operations.PasteOperation;

    import spark.components.TextInput;
    import spark.events.TextOperationEvent;

    /**
     * This is a text input component that can only input numbers.
     * A number means a real number.
     * @author Cheng Liang
     * @version 0.0.1
     */
    public class NumberInput extends TextInput
    {

        [Bindable("numberChange")]
        /**
         * Sets number as input value.
         */
        public function set number(value : Number) : void
        {
            var s : String = value.toString();
            if(text != s) {
                text = s;
                dispatchEvent(new Event("numberChange"));
            }
        }

        public function get number() : Number
        {
            return Number(text);
        }

        public function NumberInput()
        {
            super();
            this.addEventListener(TextOperationEvent.CHANGE, onTextChange);
        }

        protected function onTextChange(event : TextOperationEvent) : void
        {

            if (event.operation is PasteOperation)
            {
                TextInput(event.currentTarget).text='';
            }

            if(text == "" || text.length == 1) {
                return;
            }

            /* To allow single (.) */
            var idx : int = text.indexOf(".", 0);
            if(idx >= 0) {
                text = text.substring(0, idx + 1) + text.substring(idx + 1).replace(".", "");
            }

            /* To allow single (-) only at the 1st position*/
            if(text.lastIndexOf("-")==0)
                text ='-'+ text.substring(1);
            else if(text.lastIndexOf("-")>0)
            {
                if(text.charAt(0)=='-')
                    text ='-'+ text.substring(1).replace("-", "");
                else
                    text =text.replace("-", "");
            }

            var arr:Array = TextInput(event.currentTarget).text.split(".");
            try{
                if(arr[1] && String(arr[1]).length > 2){                        
                    TextInput(event.currentTarget).text = arr[0]+"."+String(arr[1]).slice(0,2);
                }
            }catch(err:Error){}

            this.selectRange((text.length), (text.length));
        }
    }
}

来源：https://stackoverflow.com/questions/613963/how-can-i-allow-only-one-decimal-point-in-a-textbox

标签

vb.net

textbox