Calculate only days between two different dates

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Default.aspx

ASP.NET

<table>
        <tr>
        <td>
        Star Date
        </td>
        
        <td>
         <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
         <ajaxToolkit:CalendarExtender ID="CalendarExtender1" runat="server"  Format="dd/MM/yyyy" TargetControlID="TextBox1"/>
        </td>
        </tr>
        <tr>
        <td>
        End Date
        </td>
        <td>
         <asp:TextBox ID="TextBox2" runat="server"></asp:TextBox>
       
        <ajaxToolkit:CalendarExtender ID="CalendarExtender2" runat="server" Format="dd/MM/yyyy" TargetControlID="TextBox2"/>
        <asp:ScriptManager ID="ScriptManager1" runat="server">
        </asp:ScriptManager>
        </td>
        </tr>
        <tr>
        <td>
        Total Days
        </td>
        <td>
        <asp:TextBox ID="TextBox3" runat="server"></asp:TextBox>
        </td>
        </tr>
        <tr>
        <td></td>
        <td>
         <asp:Button ID="Button1" runat="server" Text="Submit" onclick="Button1_Click" 
                Width="82px" />
        </td>
        </tr>
        </table>

Default.aspx.cs

C#

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;


public partial class Default2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
       
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        String date1 = TextBox1.Text.ToString();
        String date2 = TextBox2.Text.ToString();
      
        DateTime dt1 = DateTime.ParseExact(date1, "dd/MM/yyyy", null);
        DateTime dt2 = DateTime.ParseExact(date2, "dd/MM/yyyy", null);

        TimeSpan span = dt2.Subtract(dt1);
        TextBox3.Text = span.ToString();
      
    }
}

Show Error

C#

String was not recognized as a valid DateTime.

Posted 21-Jan-16 22:59pm

Sabhani Vipul

Updated 21-Jan-16 23:16pm

v3

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F-ES Sitecore 22-Jan-16 5:12am

Using the debugger, what is in date1 and date2?

1 solution

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OriginalGriff · Accepted Answer · 2016-01-21T23:50:00

ParseExact expects the string you pass it from the textbox to be in an exact format - no more, no less. So if the user enters "1/6/15", "01/06/15" or "22-01-2015" it will fail, and you will get the error.
Forcing users to enter in a specific format is normally not a good idea - it's best to let them enter in a format they are familiar with (and that matches the Culture setting on their machine) and then convert that with TryParse instead of using ParseExact.
And you don't need Subtract: minus will work just as well:

C#

string date1 = TextBox1.Text;
string date2 = TextBox2.Text;

DateTime dt1, dt2;
if (!DateTime.TryParse(date1, out dt1) || !DateTime.TryParse(date2, out dt2))
    {
    ... Report problem
    return;
    }

TimeSpan span = dt2 - dt1;
TextBox3.Text = span.TotalDays.ToString();

BTW: Do yourself a favour, and stop using Visual Studio default names for everything - you may remember that "TextBox8" is the mobile number today, but when you have to modify it in three weeks time, will you then? Use descriptive names - "tbMobileNo" for example - and your code becomes easier to read, more self documenting, easier to maintain - and surprisingly quicker to code because Intellisense can get to to "tbMobile" in three keystrokes, where "TextBox8" takes thinking about and 8 keystrokes...