How to pass a Null date variable to SQL Server database

Question

I am looking for the best practice, real solution, to send a Null to a SQL Server 2008 R2 database table, when a date is unknown.

I read some inputs from a formview, and a date field maybe unknown. The database allows Null values in the field but the VB to store the Null prior to a parameterized query update is not working/eludes me.

    Dim tb2 As TextBox = TryCast(FormView1.FindControl("tbPurchDate"), TextBox)
    Dim purDT As Date
    If tb2.Text = "" Then
        IsDBNull(purDT)    ' Tried this along with other possible code
    Else
        purDT = Convert.ToDateTime(tb2.Text)
    End If

Any help would be greatly appreciated.

If you mean this, I tried it....Dim purDT As Nullable(Of DateTime) — htm11h, Mar 12 '13 at 20:50

Andrew Morton · Accepted Answer · 2014-01-15T19:10:49.443

12

If the date is unknown, send DbNull.Value as the parameter's value:

If dateIsUnknown Then
    cmd.Parameters.Add(New SqlParameter _
                       With {.ParameterName = "@purDT", _
                             .SqlDbType = SqlDbType.Date, _
                             .Value = DBNull.Value})
Else
    cmd.Parameters.Add(New SqlParameter _
                       With {.ParameterName = "@purDT", _
                             .SqlDbType = SqlDbType.Date, _
                             .Value = theDateVariable})
End If

edited Jan 15 '14 at 19:10

answered Mar 12 '13 at 22:27

Andrew Morton

24,203
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Mortan, Works, clean, formatting is outside my convention but I can live with that, and it works great. Thank you very much!!! – htm11h Mar 13 '13 at 14:59
@marc11h You're welcome :) I wouldn't normally format it like that either, but it did fit into the available width. – Andrew Morton Mar 13 '13 at 15:27

Cristian Lupascu · Answer 2 · 2013-03-12T22:35:30.160

You could use the Nullable(Of Date) to allow your purDT variable to also be Nothing:

Dim purDT As Nullable(Of Date) = Nothing

If tb2.Text <> "" Then
    purDT = Convert.ToDateTime(tb2.Text)
End If

However, the magic happens when you define the SQL parameter that will hold this value. The parameter should either be DBNull.Value or a valid (non-null) Date:

' initialize connection, command...

Dim param = New SqlParameter()
param.ParameterName = "NullableDate"
param.Value = IIf(purDT Is Nothing, DBNull.Value, purDT)

cmd.Parameters.Add(param)
cmd.ExecuteNonQuery()

score 1 · Answer 3 · answered Mar 12 '13 at 21:03

It depends on the data method you are using to send the data to the server.

purDate is a variable of DateTime type and it cannot be set to null.

I suggest you use IsDate instead of testing length.

    Dim purDT As Date
    If Not IsDate(TextBox1.Text) Then
        purDT = Nothing
    Else
        purDT = Convert.ToDateTime(TextBox1.Text)
    End If

SolarBear · Answer 4 · 2013-03-12T21:00:22.093

-1

Try this :

Dim purDT As Nullable(Of Date)

If tb2.Text = "" Then
    purDT = DBNull.Value
Else
    purDT = Convert.ToDateTime(tb2.Text)
End If

edited Mar 12 '13 at 21:00

answered Mar 12 '13 at 20:52

SolarBear

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How to pass a Null date variable to SQL Server database

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