如何检查它是否为空？

Question

我从数据库中检索数据,如下所示.如何检查从数据库检索的值是否为空？

Private Function GetBatch() As DataSet
        Dim dataset As New DataSet
        Dim adapter As Data.SqlClient.SqlDataAdapter
        Dim cn As New System.Data.SqlClient.SqlConnection(connectionstring())
        GetBatchCommand.Connection = cn
        adapter = New Data.SqlClient.SqlDataAdapter(GetBatchCommand)
        adapter.Fill(dataset)
        Return dataset
End Function

Dim dataset As New DataSet
            dataset = GetBatch()

With dataset.Tables(0)

Dim PersonID As String = .Rows(int).Item("personId")

我想检查personID是否为null.怎么办？

Answer 1

尝试DataRow的IsNull方法来检查空值:

Dim isPersonIDNull As Boolean = .Rows(0).IsNull("personId")

或者使用IsDBNull方法:

Dim isPersonIDNull As Boolean = IsDBNull(.Rows(int).Item("personId"))

或者手动检查值是否等于DBNull:

Dim isPersonIDNull As Boolean = .Rows(int).Item("personId").Equals(DBNull.Value)