Create csharp LinkedList and its unit test.

codes/csharp/include/ListNode.cs

@@ -0,0 +1,68 @@
+// File: ListNode.cs
+// Created Time: 2022-12-16
+// Author: mingXta (1195669834@qq.com)
+
+namespace hello_algo.include
+{
+    /// <summary>
+    /// Definition for a singly-linked list node
+    /// </summary>
+    public class ListNode
+    {
+        public int val;
+        public ListNode next;
+
+        /// <summary>
+        /// Generate a linked list with an array
+        /// </summary>
+        /// <param name="x"></param>
+        public ListNode(int x)
+        {
+            val = x;
+        }
+
+        /// <summary>
+        /// Generate a linked list with an array
+        /// </summary>
+        /// <param name="arr"></param>
+        /// <returns></returns>
+        public static ListNode ArrToLinkedList(int[] arr)
+        {
+            ListNode dum = new ListNode(0);
+            ListNode head = dum;
+            foreach (int val in arr)
+            {
+                head.next = new ListNode(val);
+                head = head.next;
+            }
+            return dum.next;
+        }
+
+        /// <summary>
+        /// Get a list node with specific value from a linked list
+        /// </summary>
+        /// <param name="head"></param>
+        /// <param name="val"></param>
+        /// <returns></returns>
+        public static ListNode GetListNode(ListNode head, int val)
+        {
+            while (head != null && head.val != val)
+            {
+                head = head.next;
+            }
+            return head;
+        }
+
+        public override string? ToString()
+        {
+            List<string> list = new();
+            var head = this;
+            while (head != null)
+            {
+                list.Add(head.val.ToString());
+                head = head.next;
+            }
+            return string.Join("->", list);
+        }
+    }
+}