Add utilities library

Author: irvinesunday

src/Microsoft.OpenApi/Utils.cs

@@ -0,0 +1,36 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license.
+
+using System;
+
+namespace Microsoft.OpenApi
+{
+    /// <summary>
+    /// Utilities methods
+    /// </summary>
+    public static class Utils
+    {
+        /// <summary>
+        /// Check whether the input argument value is null or not.
+        /// </summary>
+        /// <typeparam name="T">The input value type.</typeparam>
+        /// <param name="value">The input value.</param>
+        /// <param name="parameterName">The input parameter name.</param>
+        /// <returns>The input value.</returns>
+        internal static T CheckArgumentNull<T>(T value, string parameterName) where T : class
+        {
+            return value ?? throw new ArgumentNullException(parameterName, $"Value cannot be null: {parameterName}");
+        }
+
+        /// <summary>
+        /// Check whether the input string value is null or empty.
+        /// </summary>
+        /// <param name="value">The input string value.</param>
+        /// <param name="parameterName">The input parameter name.</param>
+        /// <returns>The input value.</returns>
+        internal static string CheckArgumentNullOrEmpty(string value, string parameterName)
+        {
+            return string.IsNullOrEmpty(value) ? throw new ArgumentNullException(parameterName, $"Value cannot be null or empty: {parameterName}") : value;
+        }
+    }
+}