Linq-如何在where子句中使用2列

如何解决Linq-如何在where子句中使用2列

我有两个数据表，我想使用linq基于2列（col1，col2）从第一张表中选择第二张表中不存在的行

请检查以下示例

我尝试过此页面中的示例 Compare two DataTables and select the rows that are not present in second table

在示例中，它们仅使用一列

编辑1 我尝试过

        DataTable Table1 = new DataTable();
        Table1.Columns.Add("col1",typeof(string));
        Table1.Columns.Add("col2",typeof(string));

        DataRow r1 = Table1.NewRow();
        r1["col1"] = "A";
        r1["col2"] = "A-1";
        Table1.Rows.Add(r1);

        DataRow r2 = Table1.NewRow();
        r2["col1"] = "B";
        r2["col2"] = "B-2";
        Table1.Rows.Add(r2);

        DataRow r3 = Table1.NewRow();
        r3["col1"] = "C";
        r3["col2"] = "C-3";
        Table1.Rows.Add(r3);

        DataRow r4 = Table1.NewRow();
        r4["col1"] = "D";
        r4["col2"] = "D-4";
        Table1.Rows.Add(r4);

        DataRow r5 = Table1.NewRow();
        r5["col1"] = "E";
        r5["col2"] = "E-5";
        Table1.Rows.Add(r5);


        DataTable Table2 = new DataTable();
        Table2.Columns.Add("col1",typeof(string));
        Table2.Columns.Add("col2",typeof(string));

        DataRow r11 = Table2.NewRow();
        r11["col1"] = "A";
        r11["col2"] = "A-1";
        Table2.Rows.Add(r11);

        DataRow r22 = Table2.NewRow();
        r22["col1"] = "B";
        r22["col2"] = "B-2";
        Table2.Rows.Add(r22);

        DataRow r33 = Table2.NewRow();
        r33["col1"] = "C";
        r33["col2"] = "C-4";
        Table2.Rows.Add(r33);

        DataRow r44 = Table2.NewRow();
        r44["col1"] = "D";
        r44["col2"] = "DD";
        Table2.Rows.Add(r44);

        DataRow r55 = Table2.NewRow();
        r55["col1"] = "E";
        r55["col2"] = "EE";
        Table2.Rows.Add(r55);

        DataRow r66 = Table2.NewRow();
        r66["col1"] = "F";
        r66["col2"] = "FF";
        Table2.Rows.Add(r66);

示例-1

DataTable table3s = (from a in Table1.AsEnumerable()
                             where !Table2.AsEnumerable().Any(e => (e.Field<string>("col1") == a.Field<string>("col1"))
                             && (e.Field<string>("col2") == a.Field<string>("col2")))
                             select a).CopyToDataTable();

示例-2

 DataTable TableC = Table1.AsEnumerable().Where(ra => !Table2.AsEnumerable()
                            .Any(rb => rb.Field<string>("col1") == ra.Field<string>("col1")
                            && rb.Field<string>("col2") == ra.Field<string>("col2"))).CopyToDataTable();

示例1和2在没有匹配的行时给出错误

源不包含DataRows

请根据我的示例代码给出工作示例，并提出最有效的方法，因为DataTable可能包含10000行，20000行及更多的大记录

解决方法

或者使用Any：使用适当的外部联接而没有隐式循环的事物：

        var res = from a in Table1
            join b in Table2
                on (a.col1,a.col2) equals (b.col1,b.col2)
                into temp
            from b in temp.DefaultIfEmpty(default)
            where b.col2 == null
            select a;

它只是使用组合键将两个表连接在一起，并将其放入temp表中。然后，它执行外部联接（DefaultIfEmpty），并仅从Table1中获得联接返回空结果的那些条目。

,

假设您有

class Table1
{
    public string col1 { get; set; }
    public string col2 { get; set; }
}

class Table2
{
    public string col1 { get; set; }
    public string col2 { get; set; }
}

和

List<Table1> table1s = new List<Table1>();
List<Table2> table2s = new List<Table2>();

查询是

var table3s = from table1 in table1s
                where !table2s.Any(e => (e.col1 == table1.col1) && (e.col2 == table1.col2))
                select table1;

,

尝试一下。基本上，这行代码从Table1中选择了Table2中不存在“ col1”和“ col2”值的每个元素。

var results = Table1.AsEnumerable().Where(t1 => Table2.AsEnumerable().All(t2 => t2["col1"] != 
    t1["col1"] || t2["col2"] != t1["col2"]));

,

我尝试使用以下逻辑解决此问题。请让我知道我是否在这里错过了什么？

$em = $this->getDoctrine()->getManager();
$platform = $em->getRepository("AGAAnalyticsBundle:Platform")->find(1);
$platform->addProduct('05062');
$em->flush();