diff --git a/csharp/0205-isomorphic-strings.cs b/csharp/0205-isomorphic-strings.cs
new file mode 100644
index 000000000..04097c6a8
--- /dev/null
+++ b/csharp/0205-isomorphic-strings.cs
@@ -0,0 +1,29 @@
+public class Solution {
+    public bool IsIsomorphic(string s, string t) {
+        Dictionary<string, string> mapST = new Dictionary<string, string>();
+        Dictionary<string, string> mapTS = new Dictionary<string, string>();
+
+        for (int i = 0; i < s.Length; i++) {
+            string sChar = s[i].ToString();
+            string tChar = t[i].ToString();
+
+            if (mapST.ContainsKey(sChar)) {
+                if (mapST[sChar] != tChar) {
+                    return false;
+                }
+            } else {
+                mapST.Add(sChar, tChar);
+            }
+
+            if (mapTS.ContainsKey(tChar)) {
+                if (mapTS[tChar] != sChar) {
+                    return false;
+                }
+            } else {
+                mapTS.Add(tChar, sChar);
+            }
+        }
+
+        return true;
+    }
+}
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