diff --git a/cs/longest-subarray-of-1s-after-deleting-one-element.cs b/cs/longest-subarray-of-1s-after-deleting-one-element.cs
new file mode 100644
index 0000000..d36e1c9
--- /dev/null
+++ b/cs/longest-subarray-of-1s-after-deleting-one-element.cs
@@ -0,0 +1,20 @@
+public class Solution {
+    public int BitToInt(int num) => num == 0 ? 1 : 0;
+
+    public int LongestSubarray(int[] nums) {
+        var longest = 0;
+
+        var zeros = 0;
+        for (int l = 0, r = 0; r < nums.Length; ++r) {
+            zeros += BitToInt(nums[r]);
+
+            for (; zeros > 1; ++l) {
+                zeros -= BitToInt(nums[l]);
+            }
+
+            longest = Math.Max(longest, r - l);
+        }
+
+        return longest;
+    }
+}