AssetDatabase

AssetDatabase is an API which allows you to access the assets contained in your project. Among other things, it provides methods to find and load assets and also to create, delete and modify them. The Unity Editor uses the AssetDatabase internally to keep track of asset files and maintain the linkage between assets and objects that reference them. Since Unity needs to keep track of all changes to the project folder, you should always use the AssetDatabase API rather than the filesystem if you want to access or modify asset data.

The AssetDatabase interface is only available in the editor and has no function in the built player. Like all other editor classes, it is only available to scriptsA piece of code that allows you to create your own Components, trigger game events, modify Component properties over time and respond to user input in any way you like. More info
See in Glossary placed in the Editor folder (just create a folder named “Editor” in the main Assets folder of your project if there isn’t one already).

Importing an Asset

Unity normally imports assets automatically when they are dragged into the project but it is also possible to import them under script control. To do this you can use the AssetDatabase.ImportAsset method as in the example below.

using UnityEngine;
using UnityEditor;

public class ImportAsset {
    [MenuItem ("AssetDatabase/ImportExample")]
    static void ImportExample ()
    {
        AssetDatabase.ImportAsset("Assets/Textures/texture.jpg", ImportAssetOptions.Default);
    }
}

You can also pass an extra parameter of type AssetDatabase.ImportAssetOptions to the AssetDatabase.ImportAsset call. The scripting reference page documents the different options and their effects on the function’s behaviour.

Loading an Asset

The editor loads assets only as needed, say if they are added to the sceneA Scene contains the environments and menus of your game. Think of each unique Scene file as a unique level. In each Scene, you place your environments, obstacles, and decorations, essentially designing and building your game in pieces. More info
See in Glossary or edited from the InspectorA Unity window that displays information about the currently selected GameObject, Asset or Project Settings, alowing you to inspect and edit the values. More info
See in Glossary panel. However, you can load and access assets from a script using AssetDatabase.LoadAssetAtPath, AssetDatabase.LoadMainAssetAtPath, AssetDatabase.LoadAllAssetRepresentationsAtPath and AssetDatabase.LoadAllAssetsAtPath. See the scripting documentation for further details.

using UnityEngine;
using UnityEditor;

public class ImportAsset {
    [MenuItem ("AssetDatabase/LoadAssetExample")]
    static void ImportExample ()
    {
        Texture2D t = AssetDatabase.LoadAssetAtPath("Assets/Textures/texture.jpg", typeof(Texture2D)) as Texture2D;
    }
}

File Operations using the AssetDatabase

Since Unity keeps metadata about asset files, you should never create, move or delete them using the filesystem. Instead, you can use AssetDatabase.Contains, AssetDatabase.CreateAsset, AssetDatabase.CreateFolder, AssetDatabase.RenameAsset, AssetDatabase.CopyAsset, AssetDatabase.MoveAsset, AssetDatabase.MoveAssetToTrash and AssetDatabase.DeleteAsset.

public class AssetDatabaseIOExample {
    [MenuItem ("AssetDatabase/FileOperationsExample")]
    static void Example ()
    {
        string ret;
        
        // Create
        Material material = new Material (Shader.Find("Specular"));
        AssetDatabase.CreateAsset(material, "Assets/MyMaterial.mat");
        if(AssetDatabase.Contains(material))
            Debug.Log("Material asset created");
        
        // Rename
        ret = AssetDatabase.RenameAsset("Assets/MyMaterial.mat", "MyMaterialNew");
        if(ret == "")
            Debug.Log("Material asset renamed to MyMaterialNew");
        else
            Debug.Log(ret);
        
        // Create a Folder
        ret = AssetDatabase.CreateFolder("Assets", "NewFolder");
        if(AssetDatabase.GUIDToAssetPath(ret) != "")
            Debug.Log("Folder asset created");
        else
            Debug.Log("Couldn't find the GUID for the path");
        
        // Move
        ret = AssetDatabase.MoveAsset(AssetDatabase.GetAssetPath(material), "Assets/NewFolder/MyMaterialNew.mat");
        if(ret == "")
            Debug.Log("Material asset moved to NewFolder/MyMaterialNew.mat");
        else
            Debug.Log(ret);
        
        // Copy
        if(AssetDatabase.CopyAsset(AssetDatabase.GetAssetPath(material), "Assets/MyMaterialNew.mat"))
            Debug.Log("Material asset copied as Assets/MyMaterialNew.mat");
        else
            Debug.Log("Couldn't copy the material");
        // Manually refresh the Database to inform of a change
        AssetDatabase.Refresh();
        Material MaterialCopy = AssetDatabase.LoadAssetAtPath("Assets/MyMaterialNew.mat", typeof(Material)) as Material;
        
        // Move to Trash
        if(AssetDatabase.MoveAssetToTrash(AssetDatabase.GetAssetPath(MaterialCopy)))
            Debug.Log("MaterialCopy asset moved to trash");
        
        // Delete
        if(AssetDatabase.DeleteAsset(AssetDatabase.GetAssetPath(material)))
            Debug.Log("Material asset deleted");
        if(AssetDatabase.DeleteAsset("Assets/NewFolder"))
            Debug.Log("NewFolder deleted");
        
        // Refresh the AssetDatabase after all the changes
        AssetDatabase.Refresh();
    }
}

Using AssetDatabase.Refresh

When you have finished modifying assets, you should call AssetDatabase.Refresh to commit your changes to the database and make them visible in the project.