How do I check null date

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VS2015

Hi Friends,

I using for loop to compare access table date and datepicker date using following code, but I receive Null value for next loop. If it is Null then proceed to next row and read the next value and compare it. My codes are as follows:

What I have tried:

VB

Private Sub DtpFrom_LostFocus(sender As Object, e As EventArgs) Handles DtpFrom.LostFocus

	LvMasterReader = LvMasterCmd.ExecuteReader()

        For I = 0 To LEN - 1

            LvMasterReader.Read()

            If LvMasterReader("Mnt") = CmbMonth.Text And LvMasterReader("Yr") = CmbYear.Text And LvMasterReader("SAP_No") = TxtSapID.Text Then
                FND = 1
                FDT = LvMasterReader("From_Date").ToString

	' I Want to check this FDT before convertion 

	' IF IsDBNull (FDT) then
	' Proceed to next row and read the next value before comparing.
	
	' HOW CAN I DO THIS IN FOR LOOP ?
 
                FDT = CDate(FDT)
                FDT = FormatDateTime(FDT, vbShortDate)

                If FDT = FormatDateTime((DtpFrom.Value), vbShortDate) Then

                    MsgBox("Leave Already Posted.....!", vbOKOnly, "FF Leaves")
                    CmbLeaveType.Focus()
                    Exit Sub
                End If
            End If
        Next

  End Sub

Posted 22-Jul-18 3:21am

J_Mohan

Updated 22-Jul-18 10:35am

Bryian Tan

v2

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Bryian Tan · Answer 1 · 2018-07-22T10:36:00

You can use the IsDBNull function to check if the column contain any non-null value. Here is an example on how to do that. By the way what the For loop doing?

VB

Dim FDT As String
Dim fdtIndex As Integer

For I = 0 To LEN - 1
    If LvMasterReader.Read() Then

'...
'...
        fdtIndex = LvMasterReader.GetOrdinal("From_Date")

        If Not LvMasterReader.IsDBNull(fdtIndex) Then
            FDT = LvMasterReader(fdtIndex).ToString
            FDT = CDate(FDT)
            FDT = FormatDateTime(FDT, vbShortDate)
        Else
            FDT = String.Empty 'reset
        End If
'...
'...
    End If
 Next

SqlDataReader.GetOrdinal Method (String) (System.Data.SqlClient)[^]