Microsoft C# Interview Questions 2026
Published July 22, 2026 · Updated July 22, 2026
5 real C# interview questions asked at Microsoft. Upvoted by engineers who cleared the loop. Covers Technical, Screening rounds.
5 questions
152 engineers asked
239 upvotes
Company: Microsoft
Technology: C#
All C# Questions Asked at Microsoft
Microsoft
Medium
Technical round
.NETC#
Explain the difference between process and thread in Windows. What is a fiber? Describe how the .NET thread pool works and when you would use async/await vs raw Thread vs ThreadPool.
↑ 48 upvotes · 29 engineers asked this · SDE2
Microsoft
Medium
Technical round
JavaC#Python
Given a binary tree, print nodes level by level (BFS traversal). Then modify it to print alternate levels in reverse order (zigzag traversal). Analyse time and space complexity.
↑ 61 upvotes · 40 engineers asked this · SDE1
Microsoft
Hard
Technical round
JavaPythonC#
Given a 2D grid of 0s and 1s, count the number of islands. Then extend: find the largest island, and then explain how you would solve this for a streaming grid that changes in real time using a Union-Find structure.
↑ 54 upvotes · 34 engineers asked this · SDE2
Microsoft
Easy
Screening round
JavaC#Python
Find all pairs in an array that sum to a given target value. Explain the HashSet approach for O(n) time, handle duplicate pairs correctly, and discuss edge cases (negative numbers, empty array).
↑ 55 upvotes · 37 engineers asked this · SDE1
Microsoft
Medium
Technical round
2-5 yearsC#
In C#, what is the difference between Task.Wait() and await? Why does calling .Wait() on the UI thread risk a deadlock in a way that await does not?
↑ 21 upvotes · 12 engineers asked this · Senior SDE
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Frequently asked questions
Explain the difference between process and thread in Windows. What is a fiber? Describe how the .NET thread pool works and when you would use async/await vs raw Thread vs ThreadPool.
Explain the difference between process and thread in Windows. What is a fiber? Describe how the .NET thread pool works and when you would use async/await vs raw Thread vs ThreadPool.
Given a binary tree, print nodes level by level (BFS traversal). Then modify it to print alternate levels in reverse order (zigzag traversal). Analyse time and space complexity.
Given a binary tree, print nodes level by level (BFS traversal). Then modify it to print alternate levels in reverse order (zigzag traversal). Analyse time and space complexity.
Given a 2D grid of 0s and 1s, count the number of islands. Then extend: find the largest island, and then explain how you would solve this for a streaming grid that changes in real time using a Union-Find structure.
Given a 2D grid of 0s and 1s, count the number of islands. Then extend: find the largest island, and then explain how you would solve this for a streaming grid that changes in real time using a Union-Find structure.
Find all pairs in an array that sum to a given target value. Explain the HashSet approach for O(n) time, handle duplicate pairs correctly, and discuss edge cases (negative numbers, empty array).
Find all pairs in an array that sum to a given target value. Explain the HashSet approach for O(n) time, handle duplicate pairs correctly, and discuss edge cases (negative numbers, empty array).
In C#, what is the difference between Task.Wait() and await? Why does calling .Wait() on the UI thread risk a deadlock in a way that await does not?
In C#, what is the difference between Task.Wait() and await? Why does calling .Wait() on the UI thread risk a deadlock in a way that await does not?