Why my LINQ Where clause concatenating a string and call 'contains' using a value is not working?

Question

I am trying to filter data from db using two columns.

The thing is that the user only posts a single field, and I will use that field to check if there is any record on database that concatenating both columns values exist.

At the moment I have the following:

query
  .Where(x => string
     .Concat(x.Field1, " ", x.Field2)
     .Contains(parameter.MyValue, StringComparison.InvariantCultureIgnoreCase)); 

My problem is that the data is not being filtered this is weird, does anyone knows what is happening? thank you!

Answer 1

You did not mention which your db provider is. But you could try this:

query
  .Where(x => 
      ((x.Field1 ?? "") + " " + (x.Field2 ?? "")).Contains(parameter.MyValue)); 

This code assumes your parameter and its MyValue property are both not null, and the latter is also not empty.

Answer 2

Because your LINQ provider knows nothing about the Concat method. Try the same with the + operator.

Answer 3

First thing to check is ensure that the Sql (I assume you are querying a relational database) being generated is working when run directly against the database.

You could get the Sql statement either using a profiler, during a debug session in Visual Studio you may be able to get it via a trace, or my preference is to use LinqPad. Try these methods also.

Your query looks correct, I was able to get it to return results from my database.

Alternative queries:

query
  .Where(x => x.Field1.Contains(parameter.MyValue) || x.Field2.Contains(parameter.MyValue));


query.Select(x => new 
                  { 
                    Field = string.Concat(x.Field1, " ", x.Field2), 
                    RowData = x 
                  })
     .Where(x => x.Field.Contains(parameter.MyValue));