asp.net 如何使用LINQ从DataTable中删除行?

jfgube3f  于 2023-06-25  发布在  .NET
关注(0)|答案(7)|浏览(182)

我有下面的代码从DataTable中删除行:

var rows = dTable.Select("col1 ='ali'");
foreach (var row in rows)
   row.Delete();

以上代码运行良好。如何将此代码转换LINQ

kxe2p93d

kxe2p93d1#

LINQ不是删除或修改,而是查询数据。使用LINQ,您可以选择需要删除的数据,然后手动删除这些数据(例如:在foreach循环中或使用ForEach列表扩展):

var query = dTable.AsEnumerable().Where(r => r.Field<string>("col1") == "ali");

foreach(var row in query.ToList())
   row.Delete();

UPDATE:同样使用LINQ to DataSet,您可以选择应该留在表中的所有行,并从这些行创建新的DataTable:

var table = dTable.AsEnumerable()
                  .Where(r => r.Field<string>("col1") != "ali")
                  .CopyToDataTable();
xe55xuns

xe55xuns2#

尝试使用扩展方法的内联lambda代码:

dTable.AsEnumerable().Where(r => r.Field("col1") == "ali").ToList().ForEach(row => row.Delete());
  dTable.AcceptChanges();
swvgeqrz

swvgeqrz3#

使用for循环或while循环删除行,但不使用foreach
以下是非线性解决方案

dTable= dTable.Select("col1 <> 'ali'").CopyToDataTable();

LINQ

dTable = dTable.AsEnumerable().Where(r => r.Field<string>("col1") != "ali").CopyToDataTable();
8ftvxx2r

8ftvxx2r4#

var results = from row in dTable.Tables["tablename"].AsEnumerable()
          where row.Field<string>("Col1") == "ali" 
          select row;
foreach (DataRow row in results)
{
   dTable.Tables["tablename"].Remove(row);
}
6qfn3psc

6qfn3psc5#

试试这个

DataRow[] rows;
rows=dataTable.Select("UserName = 'ABC'"); // UserName is Column Name
foreach(DataRow r in rows)
r.Delete();
hiz5n14c

hiz5n14c6#

我搜索了很多地方(嗯,超过四次谷歌搜索)来寻找这个解决方案,最后我终于收集到(上面在Sergey别列佐夫斯基的帖子中)LINQ不做删除-所以你使用LINQ来选择你想要删除的行,并通过正在使用的数据库技术的“通常”机制删除它们。似乎使所有关于LINQ的数据库不可知的宣传变得很愚蠢?
这确实可行,尽管多做一些实验,人们可能能够将两个'For Each'循环减少到一个。
我有一个属性表,我想删除所有具有选定属性名(第三个关键字段)的条目,为特定的ObjectType(第一个关键字段),我想出了这个。
仅供参考,REPLY对象有点像Error对象-我只是打包了错误消息,一个二进制Pass/fail标志和一些其他东西,这样我就可以从查询中传回大量的内容,并(最终)将错误显示给用户。

' <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

    ' Default answer is 'OK'
    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
f0brbegy

f0brbegy7#

dTable.Rows.Remove(dTable.AsEnumerable().Where(r => r.Field<string>("col1") == "Ali").FirstOrDefault());

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