Read Only C# Unity

[ReadOnly] field;

ReadOnlyAttribute.cs

using UnityEngine;
public class ReadOnlyAttribute : PropertyAttribute
{
}

ReadOnlyDrawer.cs

// Put it inside Editor folder

using UnityEditor;
using UnityEngine;

[CustomPropertyDrawer(typeof(ReadOnlyAttribute))]
public class ReadOnlyDrawer : PropertyDrawer
{
	public override float GetPropertyHeight(SerializedProperty property,
											GUIContent label)
	{
		return EditorGUI.GetPropertyHeight(property, label, true);
	}

	public override void OnGUI(Rect position,
							   SerializedProperty property,
							   GUIContent label)
	{
		GUI.enabled = false;
		EditorGUI.PropertyField(position, property, label, true);
		GUI.enabled = true;
	}
}