Question

我正在经历一个我有DataTable的场景，其中有多种类型的列，我必须过滤掉Null Valued Column的数据类型，这样我就可以为它分配一些默认值，现在没有任何内容陷阱。以下是测试代码。

Public Class Form1

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
    Dim table As DataTable = GetTable()
    '
    ' We can instantiate a new object array and add it as a row.
    '
    Dim row As DataRow = table.Rows(1)
    For Each item As Object In row.ItemArray
        If TypeOf item Is Integer Then
            Console.WriteLine("Int: {0}", item)
        ElseIf TypeOf item Is String Then
            Console.WriteLine("String: {0}", item)
        ElseIf TypeOf item Is DateTime Then
            Console.WriteLine("DateTime: {0}", item)
        ElseIf TypeOf item Is System.DBNull Then
            Console.WriteLine("DBNULL {0}", item)
        End If
    Next
End Sub
Private Shared Function GetTable() As DataTable
    ' Here we create a DataTable with four columns.
    Dim table As New DataTable()
    table.Columns.Add("ID", GetType(Integer))
    table.Columns.Add("Name", GetType(String))
    table.Columns.Add("Desc", GetType(String))
    table.Columns.Add("Date", GetType(DateTime))

    ' Here we add five DataRows.
    table.Rows.Add(1, "Abc", "Cool Down", DateTime.Now)
    table.Rows.Add(2, "Chenno", "Helifire", DBNull.Value)
    Return table
End Function

结束班

我只遍历Null Valued Column Row，对于日期列，它显示＆＃34; System.DBNull＆＃34; 。我需要弄清楚这个列的数据类型。

Answer 1

我已经找到了如何使用特定列，有两种方法 1：列名称 2：或者通过该列的索引及其DataType

Dim row As DataRow = table.Rows(1)
    Dim index As Integer = 0
    For Each item As Object In row.ItemArray
        If TypeOf item Is Integer Then
            Console.WriteLine("Int: {0}", item)
        ElseIf TypeOf item Is String Then
            Console.WriteLine("String: {0}", item)
        ElseIf TypeOf item Is DateTime Then
            Console.WriteLine("DateTime: {0}", item)
        ElseIf TypeOf item Is System.DBNull Then
            Console.WriteLine("DBNULL {0}", item)
        End If
        If table.Columns(index).ColumnName.Contains("Date") Then
            'Do the stuff {Method 1}
        End If
        If table.Columns(index).DataType.ToString() = "System.DateTime" Then
            'Do The Stuff  {Method 2}
        End If
        index = index + 1
    Next

DataRow ArrayItem的NULL值为vb.net的DataType

1 个答案: