feat: add csharp solution to lc problem: No.0350 (doocs#1925)

Author: Jahir509

solution/0300-0399/0350.Intersection of Two Arrays II/README.md

@@ -224,6 +224,39 @@ class Solution {
 }
 ```
 
+### **C#**
+
+```cs
+public class Solution {
+    public int[] Intersect(int[] nums1, int[] nums2) {
+        HashSet<int> hs1 = new HashSet<int>(nums1.Concat(nums2).ToArray());
+        Dictionary<int, int> dict = new Dictionary<int, int>();
+        List<int> result = new List<int>();
+
+        foreach (int x in hs1) {
+            dict[x] = 0;
+        }
+
+        foreach (int x in nums1) {
+            if (dict.ContainsKey(x)) {
+                dict[x] += 1;
+            } else {
+                dict[x] = 1;
+            }
+        }
+
+        foreach (int x in nums2) {
+            if (dict[x] > 0) {
+                result.Add(x);
+                dict[x] -=1;
+            }
+        }
+
+        return result.ToArray();
+    }
+}
+```
+
 ### **...**
 
 ```

solution/0300-0399/0350.Intersection of Two Arrays II/README_EN.md

@@ -213,6 +213,40 @@ class Solution {
 }
 ```
 
+### **C#**
+
+```cs
+public class Solution {
+    public int[] Intersect(int[] nums1, int[] nums2) {
+        HashSet<int> hs1 = new HashSet<int>(nums1.Concat(nums2).ToArray());
+        Dictionary<int, int> dict = new Dictionary<int, int>();
+        List<int> result = new List<int>();
+
+        foreach (int x in hs1) {
+            dict[x] = 0;
+        }
+
+        foreach (int x in nums1) {
+            if (dict.ContainsKey(x)) {
+                dict[x] += 1;
+            } else {
+                dict[x] = 1;
+            }
+        }
+
+        foreach (int x in nums2) {
+            if (dict[x] > 0) {
+                result.Add(x);
+                dict[x] -=1;
+            }
+        }
+
+        return result.ToArray();
+    }
+}
+```
+
+
 ### **...**
 
 ```

solution/0300-0399/0350.Intersection of Two Arrays II/Solution.cs

@@ -0,0 +1,28 @@
+public class Solution {
+    public int[] Intersect(int[] nums1, int[] nums2) {
+        HashSet<int> hs1 = new HashSet<int>(nums1.Concat(nums2).ToArray());
+        Dictionary<int, int> dict = new Dictionary<int, int>();
+        List<int> result = new List<int>();
+
+        foreach (int x in hs1) {
+            dict[x] = 0;
+        }
+
+        foreach (int x in nums1) {
+            if (dict.ContainsKey(x)) {
+                dict[x] += 1;
+            } else {
+                dict[x] = 1;
+            }
+        }
+
+        foreach (int x in nums2) {
+            if (dict[x] > 0) {
+                result.Add(x);
+                dict[x] -=1;
+            }
+        }
+
+        return result.ToArray();
+    }
+}