Error CS2006 in Unity

[Valak296]

This error tells you that somewhere in an .rsp file, there is a -define: line without any text after the colon. So the question is: how do you fix it?

There are a few solutions depending on the situation.

If your project contains a csc.rsp or msc.rsp file with a line like -define: (but nothing written after it), you can either remove that line or replace it with something like -define:DEBUG. It is very important to know that adding .rsp does not always mean that you made this extension.You should enable the extension files to see what format they are in. Be aware that you only need one of these files.. This file should be placed in the Assets folder. It is worth noting that these files can be in folders Assent/, Library/ and Packages/, sometimes still in Temp/.

However, if the compiler still throws the same error, the problem might lie elsewhere. In my case, the issue was caused by Unity itself — during project creation (twice), Unity generated many .rsp files across the project with incomplete -define: lines.

I realized I would have to clean all of them manually. Since I’m a beginner in programming, I didn’t know it was possible to write a script that could automatically clean those lines from the necessary files.

Luckily, I had ChatGPT at hand, which explained the method and wrote a script for me — and now for you. Here it is:

import os

project_dir = "C:/UnityProject/Vorentia/UI/Screen"

for root, dirs, files in os.walk(project_dir):
    for file in files:
        if file.endswith(".rsp"):
            path = os.path.join(root, file)
            with open(path, "r", encoding="utf-8") as f:
                lines = f.readlines()

            new_lines = []
            for line in lines:
                cleaned = line.strip()
                if cleaned.startswith("-define:"):
                    # Перевіряємо, чи після -define: є хоч щось
                    if len(cleaned) > len("-define:"):
                        new_lines.append(line)
                else:
                    new_lines.append(line)

            with open(path, "w", encoding="utf-8") as f:
                f.writelines(new_lines)

print("Done!!!")

Instructions for beginners like me :)
If you don’t know Python or have no experience — don’t worry.

You need to create a plain text file and rename it to a Python script (with the .py extension).
Remember the file name and place it on your Desktop for convenience.

Next, press Win + S, search for Windows PowerShell (not the one that says "ISE"), and run it as administrator.

Then, type the following command into PowerShell (replace with your actual username and file name):

cd "C:\Users\your_user_name\Desktop"
python the_name_of_the_file_where_you_pasted_the_code_above.py

It is important to add that he does not always want to work without:

Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass

After that, all incomplete -define: lines should be removed automatically.

Note: The two methods above may not be the only solution to the problem, and they might not apply to your exact case.
But if this article — and ChatGPT — helped you, then that’s already good news.

[Talha-Dogan]

Thanks for sharing this guide! It is indeed a frustrating error caused by malformed response files.

For those who prefer to fix this directly inside Unity (without installing Python or using the command line), here is a native C# solution using EditorScripting.

You can simply create a new script named RspCleaner.cs inside any folder named Editor, and then click Tools > Clean RSP Files in the Unity menu bar.

C#
using UnityEngine;
using UnityEditor;
using System.IO;
using System.Linq;

public class RspCleaner
{
[MenuItem("Tools/Clean RSP Files")]
public static void CleanEmptyDefines()
{
// Get the project root path
string projectPath = Directory.GetCurrentDirectory();

    // Find all .rsp files in the project
    var rspFiles = Directory.GetFiles(projectPath, "*.rsp", SearchOption.AllDirectories);
    int fixedCount = 0;

    foreach (var file in rspFiles)
    {
        var lines = File.ReadAllLines(file);
        // Filter out lines that are exactly "-define:" with nothing else
        var cleanedLines = lines.Where(line => !line.Trim().Equals("-define:")).ToArray();

        // Only write back if changes were made
        if (lines.Length != cleanedLines.Length)
        {
            File.WriteAllLines(file, cleanedLines);
            fixedCount++;
            Debug.Log($"[RspCleaner] Fixed file: {file}");
        }
    }

    Debug.Log($"<b>Done!</b> Fixed {fixedCount} .rsp files.");
    AssetDatabase.Refresh();
}

}
This does the exact same text parsing logic but keeps your workflow entirely within the Unity Editor.