Linq不等于(！=)条件 [英] Linq not equal(!=) condition

问题描述

大家好，

我在使用不等于(！=)条件的lambda(或linq)中遇到问题.
这是我的代码:

Hi guys,

I have a problem in lambda(or linq) using not equal(!=) condition.
Here''s my code:

IEnumerable<DataRow> ToUpload = dtTable.Select().Where(o => o[0] != dtUploadedIDs.Select().Where(p => (string)p[1] == sTableName).Select(q => q[0]));

dtTable看起来像这样:

dtTable looks like this:

--------------------
| IndexID |  blabla
--------------------
|    1    |   asd
|    2    |   rtr
--------------------

和dtUploadedIDs像这样:

and dtUploadedIDs is like this:

---------------------
| IndexID | TableName
---------------------
|    1    |   asd
---------------------

我想删除dtTable中IndexID等于dtUploadedIDs索引ID的所有行.
它们都在DataTable中.

请帮帮我.

在此先感谢您.

I want to remove all rows in dtTable whose IndexID is equal to dtUploadedIDs Index ID.
They are both in DataTable.

Please help me.

Thanks in advance.

推荐答案

我将解决方案分为两个变量，以便更加清楚地说明，

首先，让我们获取所有ID(我想它是int类型，而不是字符串或其他任何类型):

I''ve split my solution into two variables to be more clear,

First thing, lets get all ids (I suppose it is type int, not string or any other):

var allUploaded = dtUploadedIDs.Select().Select( p => ( int )p[ 0 ] );

拥有所有ID后，我们可以检查ToUpload表中的ID是否等于其中任何一个:

After we have all ids we can check whether our id from ToUpload table equals to any of them:

var ToUpload = dtTable.Select().Where( o => !allUploaded.Contains( ( int )o[ 0 ] ) );

而已.您可以根据需要将它们组合为单个表达式.

That''s it. You can combine them in single expression if you wish.

尝试此LINQ查询

Try this LINQ query

// Select Distinct and Index ids that are only found in dtTable
var indexIDs =(from row1 in dtTable.AsEnumerable()
select new
{
    indexID1 = row1.Field<string>("IndexID"),
}).Distinct.Except(from row2 in dtUploadedIDs.AsEnumerable()
select new
{
    indexID2 = row2.Field<string>("IndexID")
}));

// Select the record based on the IndexId results
var toUpload = (from row1 in dtTable.AsEnumerable()
select new
{
    indexID = row1.Field<string>("IndexID"),
    blabla = row1.Field<string>("blabla")
}).where(r=> r.indexIDs.Contains(indexID)));

有关更多信息，请参见
101个LINQ示例:设置运算符[不同且不相同] [在DataView中查询DataRowView集合 [

For more info look
101 LINQ Samples: Set Operators [ Distinct and Except ][^]
Querying the DataRowView Collection in a DataView[^]

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