LINQ with DataSet in vb.net

Question

我想选择数据集中的所有列。数据集从数据库表派生。

这是我的代码：

  lstvCustomers.Items.Clear()
    Dim result = (From cust In dsCust.Tables(0).AsEnumerable).ToList
    'When i set where clause condition (Where cust.Field(Of String)("Ccd").Contains(txtCustID.Text))
    ' error occured in bellow line Error : The source contains not datarow
    Dim custTable As DataTable = result.CopyToDataTable
    lstvCustomers.Columns.Clear()
    For cls As Integer = 1 To custTable.Columns.Count - 1
        lstvCustomers.Columns.Add("COl - " & cls)
    Next
    Dim i As Integer = 0
    For Each row In custTable.Rows
        Dim lst As ListViewItem = lstvCustomers.Items.Add(row(0))
        For cls As Integer = 1 To custTable.Columns.Count - 1
            lst.SubItems.Add(row(cls))
        Next
        i = i + 1
    Next

输出
Col1 COl2 COl3 COL4 Col5 COl6 COL7
客户101 客户101 真正的客户101 客户101 客户101 客户101 232323

客户102 客户102 真正的客户102 客户102 客户102 客户102 234324

我想从数据集中选择所有列。帮帮我。

Answer 1

尝试：

    Dim qry = (From cust In custTable.AsEnumerable
                Where cust.Field(Of String)("Ccd").Contains(txtResults.Text)
                Select cust).ToList

这会将与条件匹配的每个数据行作为数据行列表返回，您可以在其中根据需要访问每个字段。

要将行添加到列表视图，请尝试以下操作：

For Each row In qry
    lstvCustomers.Items.Add(row.Field(Of String)("Ccd")).SubItems.Add(row.Field(Of String)("Cnm"))
Next

Answer 2

我搜索了四次以上的Google搜索）以寻找解决方案，最后我最终收集到（上图）LINQ不执行删除 - 因此您使用LINQ选择要删除的行，并通过正在使用的数据库技术的"常规"机制删除它们。似乎使所有关于 LINQ 的与数据库无关的宣传变得非常愚蠢？这个至少可以工作，尽管我将使用两个"For Each"循环，看看是否可以将其减少到一个。我有一个属性表，我想删除对象类型（第一个键字段）的所有具有选定属性名称（第三个键字段）的条目，我想出了这个。仅供参考，REPLY 对象有点像错误对象 - 我只是打包错误消息、二进制 Pass/fail 标志和其他一些东西，这样我就可以从查询中传回大量东西并（最终）向用户显示错误。

  ' <summary>
  ' The user has decided they don't want a particular property type so we delete all
  ' properties of that type in the table - belonging to any object of that ObjectType
  ' </summary>
  ' <param name="sObjectType"></param>
  ' <param name="sName"></param>
  ' <returns></returns>
  ' <remarks></remarks>
  Public Function DeleteAllPropsByName(sObjectType As String, sName As String) As Reply
    DeleteAllPropsByName = New Reply(True)
    Dim T As DataTable = mDB.DataTableImage(msTableName)
    Dim q = From rw In T.AsEnumerable
            Where rw.Field(Of String)("ObjectType") = sObjectType _
            And rw.Field(Of String)("PropName") = sName
    ' Somewhere to remember our list of target rows to delete
    Dim rows As New List(Of DataRow)
    For Each row In q
      '
      ' LINQ doesn't delete so we need to delete from the Datatable directly.
      ' If we delete here we get the collection modified error so we have to save 
      ' the datarows to ANOTHER list and then delete them from there.
      rows.Add(row)
    Next
    For Each rw As DataRow In rows
      '
      ' Call the Delete routine in my table class passing it the 
      ' primary key of the row to delete
      '
      DeleteAllPropsByName = gDB.Table(msTableName).Delete( _
                                  rw.Item("ObjectType").ToString, _
                                  CInt(rw.Item("ObjectID")), _
                                  rw.Item("PropName").ToString)
      If Not DeleteAllPropsByName.OK Then
        ' The reply object (in DeleteAllPropsByName) has all the error info so we can just
        ' exit and return it if the delete failed.
        Exit Function
      End If
    Next
  End Function

Answer 3

lstvCustomers.Items.Clear()  
Dim result = (From cust In dsCust.Tables(0).Select("Ccd LIKE '%" & txtCustID.Text & "%'")).ToList  
Dim clm As Integer = 0  
For Each row As DataRow In result  
    lstvCustomers.Items.Add(row(0))  
    lstvCustomers.Items(clm).SubItems.Add(row(1))  
    clm = clm + 1  
Next