ASP.NET Decimal.Parse()
I have problem in webpage , Visual Studio claims that problem is with this line decimal newAmount = PLNamount * Decimal.Parse(item.Value);. The solution is crushed when I choose the Current (web page is simple current converter) .
this is listing of CurrencyConverter.aspx.cs
using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
public partial class CurrencyConverter : System.Web.UI.Page
{
protected void Page_Load(Object sender, EventArgs e)
{
if (this.IsPostBack == false)
{
// The HtmlSelect control accepts text or ListItem objects.
Currency.Items.Add(new ListItem("开发者_如何学编程Euros", "0.25"));
Currency.Items.Add(new ListItem("US Dollar", "0.32"));
Currency.Items.Add(new ListItem("British Pound", "0.205"));
}
}
protected void Convert_ServerClick(object sender, EventArgs e)
{
decimal PLNamount;
bool success = Decimal.TryParse(PLN.Value,out PLNamount);
if (success)
{
PLNamount = Decimal.Parse(PLN.Value);
ListItem item = Currency.Items[Currency.SelectedIndex];
decimal newAmount = PLNamount * Decimal.Parse(item.Value); //prollematic line
Result.InnerText = PLNamount.ToString() + " Polish PLN = ";
Result.InnerText += newAmount.ToString() + " " + item.Text;
}
else Result.InnerText = "Invalid content";
}
}
This is listing of CurrencyConverter.aspx
<%@ Page Language="C#" AutoEventWireup="true"
CodeFile="CurrencyConverter.aspx.cs" Inherits="CurrencyConverter" %>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Currency Converter</title>
</head>
<body>
Simple Currency Converter in ASP.NET web forms <br />
<form id="Form1" runat="server">
<div>
Convert:
<input type="text" ID="PLN" runat="server" />
Polish PLN to Euros.
<select ID="Currency" runat="server" />
<br /><br />
<input type="submit" value="OK" ID="Convert" runat="server"
OnServerClick="Convert_ServerClick" />
<br /><br />
<div style="font-weight: bold" ID="Result" runat="server"></div>
</div>
</form>
</body>
</html>
This Code is changed listing from apress "Pro ASP.NET 3.5 in C# 2008, Second Edition" (original version) from chapter 5. Link to source code apress.com/book/downloadfile/3803 . I have exactly the same problem in the same line
Original source code from the book
aspx
<%@ Page Language="C#" AutoEventWireup="true"
CodeFile="CurrencyConverter.aspx.cs" Inherits="CurrencyConverter" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Currency Converter</title>
</head>
<body>
<form ID="Form1" method="post" runat="server">
<div style="border-right: thin ridge; padding-right: 20px; border-top: thin ridge;
padding-left: 20px; padding-bottom: 20px; border-left: thin ridge; width: 531px;
padding-top: 20px; border-bottom: thin ridge; font-family: Verdana; background-color: #FFFFE8">
Convert:
<input type="text" ID="US" runat="server" style="width: 102px" /> U.S. dollars to
<select ID="Currency" runat="server" />
<br /><br />
<input type="submit" value="OK" ID="Convert" runat="server" OnServerClick="Convert_ServerClick" />
<input type="submit" value="Show Graph" ID="ShowGraph" runat="server" OnServerClick="ShowGraph_ServerClick" />
<br /><br />
<img ID="Graph" alt="Currency Graph" scr="" runat="server" />
<br /><br />
<div style="font-weight: bold" ID="Result" runat="server"></div>
</div>
</form>
</body>
</html>
aspx.cs
using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
public partial class CurrencyConverter : System.Web.UI.Page
{
protected void Page_Load(Object sender, EventArgs e)
{
if (this.IsPostBack == false)
{
// The HtmlSelect control accepts text or ListItem objects.
Currency.Items.Add(new ListItem("Euros", "0.85"));
Currency.Items.Add(new ListItem("Japanese Yen", "110.33"));
Currency.Items.Add(new ListItem("Canadian Dollars", "1.2"));
}
Graph.Visible = false;
}
protected void Convert_ServerClick(object sender, EventArgs e)
{
decimal amount;
bool success = Decimal.TryParse(US.Value, out amount);
if (success)
{
// Retrieve the selected ListItem object by its index number.
ListItem item = Currency.Items[Currency.SelectedIndex];
decimal newAmount = amount * Decimal.Parse(item.Value);
Result.InnerText = amount.ToString() + " U.S. dollars = ";
Result.InnerText += newAmount.ToString() + " " + item.Text;
}
else
{
Result.InnerText = "The number you typed in was not in the correct format. ";
Result.InnerText += "Use only numbers.";
}
}
protected void ShowGraph_ServerClick(object sender, EventArgs e)
{
Graph.Src = "Pic" + Currency.SelectedIndex.ToString() + ".png";
Graph.Visible = true;
}
}
Problem solved
This is link to print screen with this error. http://img210.imageshack.us/f/currencyerror.png/
I think the answer is localisation based. I suspect you are parsing "0.25" as a decimal in your a culture style which uses commas as decimal separators. What you need to do is to specify what style the numbers are in so that it interprets them correctly. One way to do this is:
decimal newAmount = PLNamount * Decimal.Parse(item.Value, CultureInfo.InvariantCulture.NumberFormat)
Hopefully people will comment if there is a nicer way of doing it.
Hope that helps. I've not confirmed that this is definitely your problem but if I try to parse the number as pl-PL (just guessing you are polish from the page) then it fails for me on that line you quoted so I reckon I'm on the right lines. :)
Edit to add: The other option is to change your dropdown to have values like "0,25" which should parse correctly. However, I personally would prefer to use the CultureInfo option.
Interestingly when I enter numbers into the box on the page it seems to recognise "0.9" and "0,9" as the same thing. Not sure why it works there but I guess its related to tryParse and Parse workign subtly differently.
You don't need to do both:
bool success = Decimal.TryParse(PLN.Value,out PLNamount);
if (success)
{
PLNamount = Decimal.Parse(PLN.Value);
If the TryParse succeeded then PLNamount will contain the correct value. Check the MSDN documentation for TryParse.
Also:
ListItem item = Currency.Items[Currency.SelectedIndex];
decimal newAmount = PLNamount * Decimal.Parse(item.Value); //prollematic line
if the value in item isn't a string representing a number Parse will throw an exception. For safety you should use TryParse on this value as well (if it's not already a numeric type of course).
you should delete the following line
PLNamount = Decimal.Parse(PLN.Value);
if(success) ... then PLNamount are already parsed, it is an out parameter...
Parse throws an exception if the value being parsed isn't a decimal. TryParse is safer in that respect; it returns a bool if it is a decimal, and returns the value through an output parameter, but you should check that TryParse returns true.
if (decimal.TryParse("12", out decValue)) { .. }
Using TryParse for the item check, where the error occurs, too may help...
The problem is't solved . item.Value is string in 100% //debuger confirms that.
I don't know what I have to do.
the answer is this, assuming it's a value from a DropDown that always contains percentages.
decimal ItemValue = Decimal.Parse(Item.Value.Substring(0, Item.Value.IndexOf('%')));
It strips the % from the string and then converts the remainder to a decimal.
If you look at your debug, item.value = "US Dollar". This is a string value, you've probably want the "Text" property.
加载中,请稍侯......
精彩评论