Linq query built in foreach loop always takes parameter value from last iteration

Question

I have a List containing several keywords. I foreach through them building my linq query with them like so (boiled down to remove the code noise):

List

        

Answer 1

You're reusing the same variable (key) in your lambda expression.

See my article on anonymous methods for more details, and there are a number of related SO questions too:

• LINQ to SQL bug (or very strange feature)...
• Local variables with delegates
• C# captured variable in a loop
• C# gotcha answer
• Building a LINQ query programmatically without local variables tricking me

The simple fix is to copy the variable first:

List keys = FillKeys()
foreach (string key in keys){
    string copy = key;
    q = q.Where(c => c.Company.Name.Contains(copy));
}