vérifier si la colonne de date dans datatable est nulle

Question

Dim dr As SqlDataReader = cmd.ExecuteReader(CommandBehavior.CloseConnection)
Dim dt As DataTable = New DataTable()
dt.Load(dr)

For Each row As DataRow In dt.Rows

    Dim dob_str As String = ""

    'code to check if row.Field(Of Date)("DOB") is dbnull
    'if not dbnull then dob_str = row.Field(Of Date)("DOB")

Next

Comment puis-je vérifier si le Date tapez une colonne pour chaque ligne du DataTable est vide?

J'ai essayé

    If Not row.Field(Of Date)("DOB") = Nothing Then
        dob_str = row.Field(Of Date)("DOB")
    End If

et

    Dim nullCheck As Boolean = IsDBNull(row.Field(Of Date)("DOB"))
    If nullCheck = False Then
        dob_str = row.Field(Of Date)("DOB")
    End If

mais ils ont tous abouti au Cannot cast DBNull.Value to type 'System.DateTime'. Please use a nullable type. pendant l'exécution.

Answer 1

Utiliser un Nullable taper

If row.Field(Of Date?)("DOB") IsNot Nothing Then
    dob_str = row.Field(Of Date)("DOB")
End If

Ou

If row.Field(Of Date?)("DOB").HasValue Then
    dob_str = row.Field(Of Date)("DOB")
End If

Ou utiliser IsNull

If Not row.IsNull("DOB") Then
    dob_str = row.Field(Of Date)("DOB")
End If