Microsoft .NET Code Analysis: Add Explicit Cast in foreach() Loops

When looping over a collection in a foreach() loop, there could be an issue with casting that coders might not be aware of. Let’s look at the code that demonstrates this issue.

foreach (DataInstance item in instances.DataItemInstances) 
{
    if (item.Definition != null && item.Definition.External) 
    {
        results.Add(item);
    }
}

Upon examining this code, it’s not immediately apparent that DataItemInstances is a collection type implementing ICollection<> of DataInstance. The issue lies in the fact that it obscures a potentially problematic cast, which may lead to runtime issues. I assume that most developers reviewing this code might not readily recognize this issue; I had to delve deeper to discern it.

To rectify this code, you can simply add an explicit cast, as demonstrated in the refactored code below:

foreach (var item in instances.DataItemInstances.Cast<DataInstance>())
{
    if (item.Definition is not null && item.Definition.External) 
    {
        results.Add(item);
    }
}

This code can be further simplified by employing LINQ, as demonstrated below:

results.AddRange(instances.DataItemInstances.Cast<DataInstance>()
  .Where(item => item.Definition is not null &&
  item.Definition.External));

Utilizing AddRange() can significantly enhance the efficiency of this code!

This is related to violation IDE0220 and this is how I have it setup in my .editorConfig: dotnet_diagnostic.IDE0220.severity = warning

Summary

While reviewing the codebase I utilized for this article, I discovered 98 occurrences where the code needs to be fixed.

For further guidance and insights, I highly recommend obtaining a copy of my book, “Rock Your Code: Coding Standards for Microsoft .NET” available on Amazon.com. Additionally, to explore more performance tips for .NET, I encourage you to acquire the 3rd edition of “Rock Your Code: Code & App Performance for Microsoft .NET” also available on Amazon.com.

To analyze your code using the same settings I used in these articles, I encourage you to incorporate my EditorConfig file. It can be found at the following link: https://bit.ly/dotNetDaveEditorConfig. I update this file quarterly, so remember to keep yours up to date as well. I hope you will check out my OSS project Spargine by using this link: https://bit.ly/Spargine.

Please feel free to leave a comment below. I would appreciate hearing your thoughts and feedback.

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