diff --git a/cs/max-consecutive-ones-iii.cs b/cs/max-consecutive-ones-iii.cs
new file mode 100644
index 0000000..5effc2a
--- /dev/null
+++ b/cs/max-consecutive-ones-iii.cs
@@ -0,0 +1,22 @@
+public class Solution {
+    public int LongestOnes(int[] nums, int k) {
+        int maxLength = 0;
+
+        int zeros = 0;
+        for (int i = 0, j = 0; j < nums.Length; ++j) {
+            if (nums[j] == 0) {
+                ++zeros;
+            }
+
+            for (; zeros > k; ++i) {
+                if (nums[i] == 0) {
+                    --zeros;
+                }
+            }
+
+            maxLength = Math.Max(maxLength, j - i + 1);
+        }
+
+        return maxLength;
+    }
+}