如何使用通配符比较两个数据表？ [英] How to compare two datatables using wildcards?

问题描述

大家好，

我必须使用LINQ比较两个数据表

Hi All,
I have to compare two datatables using LINQ

// compare if fieldsforDynamicGroup have Already groups

            DataTable merged = (from a in fieldsforDynamicGroup.AsEnumerable()
                                join b in Dtlists.AsEnumerable()
                                on a["FieldName"].ToString() equals           b["ListName"].ToString()
                                into g
                                where g.Count() > 0
                                select a).CopyToDataTable();

但问题是我无法直接加入[FieldName]。ToString（）等于b [ListName]。ToString（）



值FieldName列的结果类似于A / $
中的Facebook链接，而ListName就像昨天有Facebook链接更改的所有新兵中的B



我如何在通配符%%的基础上加入...是否有任何性能下降？

请帮忙！

but the problem is that i can't directly join a["FieldName"].ToString() equals b["ListName"].ToString()

the values of FieldName column is like "Facebook Link" in A
and ListName is like "All recruits who had Facebook Link change yesterday" in B

How can i join on the basis of wildcards %% ...Is there any performance degradation??
Please help!

推荐答案

你可以用LINQ做它，但它不漂亮：

You can do it with LINQ, but it's not pretty:

DataTable merged = fieldsforDynamicGroup.AsEnumerable()
    .Where(a => Dtlists.AsEnumerable()
        .Select(b => b.Field<string>("ListName") ?? string.Empty)
        .Any(list => list.Contains(a.Field<string>("FieldName")))
        
        // Or:
        // .Any(list => list.IndexOf(a.Field<string>("FieldName"), StringComparison.CurrentCultureIgnoreCase) != -1)
    )
    .CopyToDataTable();

你不能用Linq Join来做，因为Linq Join绝对需要比较连接列的存在等于或不等。



看起来你想要来自A的所有记录，其中FieldName出现在B的任何ListName中。我的第一个想法是：

You can't do it with a Linq Join because a Linq Join absolutely requires that the joined columns are compared for being equal or not.

Looks like you want all records from A where "FieldName" occurs in any "ListName" of B. My first idea would be:

var distinctListNames = Dtlists.AsEnumerable()
          .Select(r => r.Field<string>("ListName").ToUpper()).Distinct();

string joinedListNames = String.Join("

，distinctListNames）;

foreach （DataRow row in fieldsforDynamicGroup.Rows）
{
if （joinedListNames.Contains（row.Field< string>（ FieldName）。ToUpper（）））
{
// 对行做点什么
}
}

", distinctListNames); foreach(DataRow row in fieldsforDynamicGroup.Rows) { if(joinedListNames.Contains(row.Field<string>("FieldName").ToUpper())) { // do something with the row } }

The "

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