𝐖𝐚𝐧𝐭 𝐭𝐨 𝐤𝐧𝐨𝐰 𝐂𝐨𝐮𝐧𝐭 𝐕𝐬 𝐂𝐨𝐮𝐧𝐭() 𝐢𝐧 𝐂# 𝐋𝐢𝐬𝐭<𝐓>? 𝐋𝐞𝐭’𝐬 𝐝𝐢𝐯𝐞 𝐢𝐧.

𝐖𝐡𝐚𝐭 𝐢𝐬 𝐂𝐨𝐮𝐧𝐭 𝐢𝐧 𝐋𝐢𝐬𝐭<𝐓>?
Count is a property of many collections in .Net and its value represents the number of elements in the collection. Its time complexity is O(1).

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𝐖𝐡𝐚𝐭 𝐢𝐬 𝐂𝐨𝐮𝐧𝐭() 𝐢𝐧 𝐋𝐢𝐬𝐭<𝐓>?
Count() is LINQ extension method for counting elements of a List.
At first, LINQ checks the type, if it is type of collection, it uses the count property. Otherwise, it iterates through all elements to count them. Its time complexity is O(n).

💯𝐃𝐨 𝐰𝐞 𝐫𝐞𝐚𝐥𝐥𝐲 𝐜𝐚𝐫𝐞 𝐭𝐡𝐞 𝐝𝐢𝐟𝐟𝐞𝐫𝐞𝐧𝐜𝐞?
Yes! For large datasets, it’s better to use the Count property instead of the Count() method whenever possible, because Count() still has the overhead of checking the type and calling the property.

❓ 𝐇𝐚𝐯𝐞 𝐲𝐨𝐮 𝐞𝐯𝐞𝐫 𝐟𝐚𝐜𝐞𝐝 𝐰𝐢𝐭𝐡 𝐬𝐮𝐜𝐡 𝐩𝐞𝐫𝐟𝐨𝐫𝐦𝐚𝐧𝐜𝐞 𝐢𝐬𝐬𝐮𝐞? 𝐒𝐡𝐚𝐫𝐞 𝐲𝐨𝐮𝐫 𝐞𝐱𝐩𝐞𝐫𝐢𝐞𝐧𝐜𝐞.