Comparing two dates in VB.Net?

Question

1.00/5 (2 votes)

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I have this code that compare a date from gridview to date.today
but it seems not working

SQL

"select * from out_logtable  order by outid desc limit 1")
DataGridView1.DataSource = Me.BindingSource1
DataGridView1.AutoGenerateColumns = True
Dim x As String = DateAndTime.Today.ToString("d")
Dim y As String = DataGridView1.Rows(0).Cells(2).Value.ToString
If DataGridView1.Rows(0).Cells(1).Value <> "admin" Then
    If x.ToString > y.ToString Then
        ExecuteSQL(1, "Update login_table set hour = '2' ")
    End If
Else

End If

Posted 6-Oct-14 16:41pm

NekoNao

Updated 8-Jun-20 8:35am

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3 solutions

Solution 1

Compares two dates?? No you don't. You have to code that compares two STRINGS, not dates. The comparison is not the same.

Convert the values to DateTime, not Strings.

Posted 6-Oct-14 17:48pm

Dave Kreskowiak

Comments

Sergey Alexandrovich Kryukov 7-Oct-14 0:36am

5, but the answer needs to be continued; I've done it in Solution 2. :-)
—SA

Dave Kreskowiak 7-Oct-14 7:27am

Yeah I was short on time.

Maciej Los 7-Oct-14 1:55am

Good point, a 5!

Solution 2

To continue Solution 1:

…and then compare instanced of the structure System.DateTime using the operator '=' or '<>' which means "same moment of time" or "not the same moment of time".
Note that you can also use '<' (sooner than), '>' (later than), '>=' (not sooner than), '<=' (not later than).

Please see: http://msdn.microsoft.com/en-us/library/system.datetime%28v=vs.110%29.aspx[^].

Also, I don't know what is your binding source, but if you use a database, don't store data related to time as string data. For these purposes, there are special data types, such as DATE.

—SA

Posted 6-Oct-14 18:35pm

Sergey Alexandrovich Kryukov

Updated 6-Oct-14 20:20pm

v4

Comments

Maciej Los 7-Oct-14 2:15am

It's VB.NET, not C#. Simple '=' would be enough.

Sergey Alexandrovich Kryukov 7-Oct-14 2:20am

Ah... well, thank you. Fixed.
—SA

Maciej Los 7-Oct-14 2:21am

Now, it's correct. 5ed!
Please, see my answer.

Sergey Alexandrovich Kryukov 7-Oct-14 2:23am

Thank you, Maceij, especially for a fix (one more fix is C# "!=").
—SA

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Maciej Los · Accepted Answer · 2014-10-06T20:20:00

VB.NET 'knows' Date data type[^]. It holds dates from January 1 of the year 0001 through December 31 of the year 9999, and times from 12:00:00 AM (midnight) through 11:59:59.9999999 PM.

Example 1 - using simple '=' operator:

VB

Dim a As Date = CDate("2014-09-12"), b As Date = Date.Now

If a = b Then
    Console.WriteLine("Dates are equal {0}={1}", a, b)
Else
    Console.WriteLine("Dates aren't equal {0}<>{1}", a, b)
End If

Console.ReadKey()

Example 2 - using Compare method[^]:

VB

Dim date1 As Date = #08/01/2009 12:00AM#
Dim date2 As Date = #08/01/2009 12:00PM#
Dim result As Integer = DateTime.Compare(date1, date2)
Dim relationship As String

If result < 0 Then
   relationship = "is earlier than"
ElseIf result = 0 Then
   relationship = "is the same time as"
Else
   relationship = "is later than"
End If

Console.WriteLine("{0} {1} {2}", date1, relationship, date2)

Example 3 - using DateDiff function[^]:

VB

Dim firstDate, msg As String
Dim secondDate As Date
firstDate = InputBox("Enter a date")
Try
    secondDate = CDate(firstDate)
    msg = "Days from today: " & DateDiff(DateInterval.Day, Now, secondDate)
    MsgBox(msg)
Catch
    MsgBox("Not a valid date value.")
End Try

Note: As is explained here: Data Type Summary (Visual Basic)[^], Date data type uses DateTime structure - to put it simply.