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How do I compare the dates in text boxes.

Posted on 2011-02-21
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Last Modified: 2013-12-17
How would I write this.  I’m trying to compare  the dates in two text boxes.  This is what I have, what’s wrong with it.

errors: invalid expression

Thanks!


string aa = TextBox1.Text.Trim();
        string bb = TextBox2.Text.Trim();
        if (aa =< bb)
        {
            Label6.Text = "Start date can not be earlier than today’s date";
            
        }

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Question by:bmanmike39
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11 Comments
 
LVL 29

Expert Comment

by:Paul Jackson
ID: 34948144
try this :
if (aa <= bb)
0
 
LVL 29

Expert Comment

by:Paul Jackson
ID: 34948184
however you would be better doing this :

string aa = TextBox1.Text.Trim(); 
        string bb = TextBox2.Text.Trim(); 

        datetime startDate;
        datetime endDate;
        startDate = new DateTime();
        endDate = new DateTime();
        startDate = DateTime.ParseExact(aa, "yyyy-MM-dd HH:mm tt", null);
        endDate = DateTime.ParseExact(bb, "yyyy-MM-dd HH:mm tt", null);
        if (DateTime.Compare(startDate,endDate) < 0 ) 
        { 
            Label6.Text = "Start date can not be earlier than today’s date"; 
             
        }

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Here is a link explaining DateTime.Compare : http://msdn.microsoft.com/en-us/library/system.datetime.compare.aspx
0
 
LVL 13

Expert Comment

by:agarwalrahul
ID: 34948364
Another way of doing this through AJAX is :

Date Formats for Ajax CalendarExtender Control

Format=”MMMM d, yyyy”  Result is April 28, 1906

=”dd/MM/yyyy”    Result is 23/11/2008

=”MM/dd/yyyy”    Result is 12/28/2008

=”dd-MMM-yyyy” Result is 23-Mar-2008

Comparing Two dates

If second textbox1(DespatchOrder) date value is less than to first textbox2(OrderTaken) date value then alert box will

display “Check date values”.This TextBox2_TextChanged event is fired when textbox2 is less than textbox1 date value.

Default.aspx Page: When using ajax controls paste script manager in aspx pages top. Check Date Formats in ajax calender
must be in dd/MM/yyyy

Ajax CalendarExtender1 both PopupButtonID=”TextBox1¿    and  TargetControlID=”TextBox1¿

Ajax CalendarExtender2 both PopupButtonID=”TextBox2¿    and  TargetControlID=”TextBox2¿

When you click Textbox1 or Textbox2 Calender control will popup you can choose the dates from there

Design Code

<table style=”border: 1px solid #000000; font-family: Arial, Helvetica, sans-serif; font-size: 9pt; background-color:

#E6E6E6¿>
<tr>
<td>OrderTaken</td>
<td>
<asp:TextBox ID=”TextBox1¿ runat=”server”></asp:TextBox>

<cc1:CalendarExtender ID=”CalendarExtender1¿ runat=”server” Format=”dd/MM/yyyy”
PopupButtonID=”TextBox1¿ TargetControlID=”TextBox1¿>
</cc1:CalendarExtender>

</td>
</tr>

<tr>
<td>
DespatchOrder</td>
<td><asp:TextBox ID=”TextBox2¿ runat=”server” AutoPostBack=”True”
ontextchanged=”TextBox2_TextChanged”></asp:TextBox>

<cc1:CalendarExtender ID=”CalendarExtender2¿ runat=”server” Format=”dd/MM/yyyy”
PopupButtonID=”TextBox2¿ TargetControlID=”TextBox2¿ >
</cc1:CalendarExtender>

</td>
</tr>

</table>

Default.aspx.cs code: Double click in TextBox2

protected void TextBox2_TextChanged(object sender, EventArgs e)
{
DateTime a = DateTime.Parse(TextBox1.Text);
DateTime b = DateTime.Parse(TextBox2.Text);

if (a > b)
{
Response.Write(”<script>alert(’Check date ranges to OrderTaken and OrderDespatch’);</script>”);
TextBox2.Text=””;
}
}

***Now Run the project Enter Textbox1 value as 09-02-2008

TextBox2 value as 02-02-2008

then textbox changed event fires and popup alert message “check date ranges to orderTaken and orderDespatch”

Note: You can write in this format also javascript alert message

Response.Write(”<script language=’javascript’>”);
Response.Write(”alert(’Please Check date ranges to OrderTaken and OrderDespatch.’);”);
Response.Write(”return false;”);
Response.Write(”<” + “/script>”);

Note: You can compare date formats like above figure but change the ajax calender control formats i.e Format=”dd-MMM-yyyy”
<cc1:CalendarExtender ID=”CalendarExtender1¿ runat=”server” Format=”dd-MMM-yyyy”
PopupButtonID=”TextBox1¿ TargetControlID=”TextBox1¿>
</cc1:CalendarExtender>

Similarly for calenderExtender2 Format=”dd-MMM-yyyy”
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Expert Comment

by:ninusajil
ID: 34948529
DateTime startdate=DateTime.ParseExact(TextBox1.Text,"dd/mm/yyyy",null);
            DateTime enddate = DateTime.ParseExact(TextBox2.Text, "dd/mm/yyyy", null);
            if (enddate > startdate)
            {
                //process
            }
0
 
LVL 44

Expert Comment

by:AndyAinscow
ID: 34949206
I would suggest you use Datetime picker controls for entering the dates on your form (unless there is a good reason they would not be suitable).  By using those it is impossible for the user to enter an incorrect date - with a text box one could enter, by mistake, 30.02.2010 (February never has 30 days)
0
 
LVL 8

Accepted Solution

by:
Anurag Agarwal earned 500 total points
ID: 34950021
hello bmanmike39 !!

I think u only need this ..........

Dim dt1, dt2 As New DateTime
        dt1 = TextBox1.Text
        dt2 = TextBox2.Text
        If DateTime.Compare(dt1, dt2) = 0 Then
            Response.Write("Same Date Time")
        ElseIf DateTime.Compare(dt1, dt2) < 0 Then
            Response.Write("dt2 is bigger")
        ElseIf DateTime.Compare(dt1, dt2) > 0 Then
            Response.Write("dt1 is bigger")
        End If

0
 
LVL 7

Expert Comment

by:kovilpattiBalu
ID: 34950566
can use .. Convert.ToDateTime() also
0
 
LVL 7

Expert Comment

by:mr_nadger
ID: 34950782
go with Kovil's Convert suggestion, just be sure to validate the contents of the boxes first.
0
 

Author Comment

by:bmanmike39
ID: 34961546
DateTime startDate = DateTime.ParseExact(TextBox1.Text, "dd/mm/yyyy", null);
        DateTime endDate = DateTime.ParseExact(TextBox2.Text, "dd/mm/yyyy", null);
        if (endDate == startDate)
        {
            Label6.Text = "End date can not be equal to start date";
       }

Error:  String was not recognized as a valid DateTime.

0
 
LVL 44

Expert Comment

by:AndyAinscow
ID: 34961585
>>Error:  String was not recognized as a valid DateTime.

That is why I made my earlier comment:

I would suggest you use Datetime picker controls for entering the dates on your form (unless there is a good reason they would not be suitable).  By using those it is impossible for the user to enter an incorrect date - with a text box one could enter, by mistake, 30.02.2010 (February never has 30 days)
0
 

Author Closing Comment

by:bmanmike39
ID: 34987576
Thanks!
0

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