create HLSL file in Unity

ShaderUtility.cs

using UnityEditor;
using System.IO;
using System.Linq;

namespace TKMNY.Editor
{
    public static class ShaderUtility
    {
        private const string DefaultHLSLTemplate = @"
#ifndef <TemplateName>_INCLUDED
#define <TemplateName>_INCLUDED

#endif
";

        [MenuItem("Assets/Create/TKMNY/HLSL", false, 1)]
        static void CreateHLSLFile()
        {
            string folderPath = "Assets/";
            if (Selection.activeObject != null)
            {
                folderPath = AssetDatabase.GetAssetPath(Selection.activeObject);
                if (Selection.activeObject.GetType() != typeof(DefaultAsset))
                {
                    folderPath = Path.GetDirectoryName(folderPath);
                }
            }
            else if (Selection.assetGUIDs.Length > 0)
            {
                folderPath = AssetDatabase.GUIDToAssetPath(Selection.assetGUIDs[0]);
            }

            folderPath = folderPath.Replace('\\', '/');

            var chosenFilePath = EditorUtility.SaveFilePanelInProject("Save HLSL File", "", "hlsl", "Save HLSL file", folderPath);

            if (!string.IsNullOrEmpty(chosenFilePath))
            {
                var chosenFileName = Path.GetFileNameWithoutExtension(chosenFilePath).Replace(" ", "");
                var template = DefaultHLSLTemplate;
                template = template.Replace("<TemplateName>", ConvertToScreamingCase(chosenFileName));

                File.WriteAllText(chosenFilePath, template, System.Text.Encoding.UTF8);

                AssetDatabase.ImportAsset(chosenFilePath, ImportAssetOptions.Default);
            }
        }

        static string ConvertToScreamingCase(string str)
        {
            return string.Concat(str.Select((x, i) => i > 0 && char.IsUpper(x) ? "_" + x.ToString() : x.ToString())).ToUpper();
        }
    }
}