Except keyword issue in LINQ

Question

I want to capture the column names which needs to be added to the SQL table in order to insert the data.

Columnspresent-- List of all columns in the file ("Node", "Logtime", "Reason","ID","Comments")

existingtablecolumnsPresent -- List of all columns in the existing table in SQL("Node","Value","Reason","ID","Comments","logtime")

columnsNotPresent -- List of columns that needs to be added to the SQL table ( have to get "Value" in the output but not getting)..

 List<string> columnsPresent = 
          dt.Columns.Cast<DataColumn>()
         .Select(a => a.ColumnName.ToLower())
         .ToList();

 List<string> existingtablecolumnsPresent = 
          existingtable.Columns.Cast<DataColumn>()
         .Select(a => "[" + a.ColumnName.ToLower() + "]")
         .ToList();

 List<string> columnsNotPresent = 
         columnsPresent.OrderBy(t => t)
        .Except(existingtablecolumnsPresent.OrderBy(t => t))
        .ToList();

The above code is not giving the correct results if there is change in order of columns .Please advise.

read this: http://stackoverflow.com/questions/16824749/using-linq-except-not-working-as-i-thought. — Lucian Bumb, Jul 22 '16 at 16:09

Ciro Corvino · Accepted Answer · 2016-08-10T22:18:28.627

0

you may try this (it needn't order by..)

List<string> existingtablecolumnsPresentNoSqrBr = new List<string>();
existingtablecolumnsPresent.ForEach(c => {
               c = c.Replace("[", string.Empty); 
               c = c.Replace("]",string.Empty);
               existingtablecolumnsPresentNoSqrBr.Add(c);
               });

List<string> columnsNotPresent = 
            columnsPresent.Except(existingtablecolumnsPresentNoSqrBr)
            .ToList();

really, if you avoid to .Select(a => "[" + a.ColumnName.ToLower() + "]") you can use the second query directly on existingtablecolumnsPresent..

edited Aug 10 '16 at 22:18

answered Jul 22 '16 at 18:13

Ciro Corvino

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@user1046415 Hi, may you give me any feedback please? – Ciro Corvino Jul 24 '16 at 19:37
what does nameColT mean in the above query? – user1046415 Aug 10 '16 at 19:31
sorry, it was a name not very readable used in my test.. I forget to change it with the more meaningful name "existingtablecolumnsPresentNoSqrBr" (a bit long really :) ) – Ciro Corvino Aug 10 '16 at 22:22

Except keyword issue in LINQ

1 Answers1