我有以下代码输出数字“ 40”：

Hashtable ht = new Hashtable();
ht.Add("numRooms", pageData.Property["romtotalt"].ToString());
string str = ht["numRooms"].ToString();
lblMigrate.Text = i.ToString();

然后，我尝试将字符串转换为int，并且出现异常/错误：

Hashtable ht = new Hashtable();
ht.Add("numRooms", pageData.Property["romtotalt"].ToString());
string str = ht["numRooms"].ToString();
int i = Convert.ToInt32(str);  // <-- This is where it fails I t hink. But why??
lblMigrate.Text = i.ToString();

这是我收到的错误消息：

Server Error in '/' Application.
Input string was not in a correct format.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.FormatException: Input string was not in a correct format.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:

[FormatException: Input string was not in a correct format.]
   System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal) +7469351
   System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info) +119
   development.templates.HotellGuide.btnMigrateHotels_Click(Object sender, EventArgs e) +956
   System.Web.UI.WebControls.Button.OnClick(EventArgs e) +111
   System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +110
   System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
   System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
   System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565


Version Information: Microsoft .NET Framework Version:2.0.50727.3082; ASP.NET Version:2.0.50727.3082

我不明白怎么了 我以前多次将int字符串转换为int，并且从未发生此问题。

请帮忙 ：）

更新资料

我找到了解决方案。我不知道为什么这行得通.....但是行得通…
我将转换放入Try Catch中，现在就行了。图一出：op

int numRooms = 0;
int numAllergyRooms = 0;

try
{
    numRooms = Convert.ToInt32(newHotel["numRooms"].ToString().Trim());
    numAllergyRooms = Convert.ToInt32(newHotel["numAllergyRooms"].ToString().Trim());
}
catch (Exception ex)
{
    Console.WriteLine("{0} Exception caught.", ex);
}