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Editorial Team
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Asked: 2026-05-13T14:27:24+00:00

On a LINQ-result you like this: var result = from x in Items select

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On a LINQ-result you like this:

var result = from x in Items select x;
List<T> list = result.ToList<T>();

However, the ToList<T> is Really Slow, does it make the list mutable and therefore the conversion is slow?

In most cases I can manage to just have my IEnumerable or as Paralell.DistinctQuery but now I want to bind the items to a DataGridView, so therefore I need to as something else than IEnumerable, suggestions on how I will gain performance on ToList or any replacement?

On 10 million records in the IEnumerable, the .ToList<T> takes about 6 seconds.

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1 Answer

  1. Editorial Team

    .ToList() is slow in comparison to what?

    If you are comparing 

    var result = from x in Items select x;
List<T> list = result.ToList<T>();

    to

    var result = from x in Items select x;

    you should note that since the query is evaluated lazily, the first line doesn’t do much at all. It doesn’t retrieve any records. Deferred execution makes this comparison completely unfair.

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