tui-cs/Terminal.Gui · error · InvalidOperationException

{schemeName}: Does not exist in Schemes.

Error message

{schemeName}: Does not exist in Schemes.

What it means

RemoveScheme was called with a name that is neither a built-in scheme nor present in the current schemes dictionary. You can only remove a scheme that was previously added via AddScheme and still exists.

Source

Thrown at Terminal.Gui/Configuration/SchemeManager.cs:105

            GetSchemes () [schemeName] = scheme;
        }
    }

    /// <summary>
    ///     Removes a Scheme from <see cref="SchemeManager"/>.
    /// </summary>
    /// <param name="schemeName"></param>
    /// <exception cref="InvalidOperationException">If the scheme is a built-in Scheme or was not previously added.</exception>
    public static void RemoveScheme (string schemeName)
    {
        if (SchemeNameToSchemes (schemeName) is { })
        {
            throw new InvalidOperationException ($@"{schemeName}: Cannot remove a built-in Scheme.");
        }

        if (!GetSchemes ().TryGetValue (schemeName, out _))
        {
            throw new InvalidOperationException ($@"{schemeName}: Does not exist in Schemes.");
        }

        GetSchemes ().Remove (schemeName);
    }

    /// <summary>
    ///     Gets the <see cref="Scheme"/> for the specified <see cref="Drawing.Schemes"/>.
    /// </summary>
    /// <param name="schemeName"></param>
    /// <returns></returns>
    /// <exception cref="ArgumentException"></exception>
    public static Scheme GetScheme (Schemes schemeName)
    {
        // Convert schemeName to string via Enum api
        string? schemeNameString = SchemesToSchemeName (schemeName);

        return schemeNameString is null ? throw new ArgumentException ($"Invalid scheme name: {schemeName}") : GetSchemesForCurrentTheme () [schemeNameString]!;
    }

View on GitHub (pinned to 2e47b11478)

Solutions

1. Verify the scheme exists with TryGetScheme or GetSchemes().ContainsKey(name) before removing.
2. Guard removal with an existence check.

Example fix

// before
SchemeManager.RemoveScheme ("myTheme");
// after
if (SchemeManager.TryGetScheme ("myTheme", out _))
{
    SchemeManager.RemoveScheme ("myTheme");
}

if (SchemeManager.TryGetScheme (name, out _))
{
    SchemeManager.RemoveScheme (name);
}

try { SchemeManager.RemoveScheme (name); }
catch (InvalidOperationException ex) when (ex.Message.Contains ("Does not exist"))
{ /* already removed or never added; nothing to do */ }

When it happens

Trigger: Calling RemoveScheme with a typo, or removing a scheme that was already removed, or before it was added.

Common situations: Double-removal; cleanup logic that does not track current state; misspelled scheme name.

Related errors

• {schemeName}: Cannot remove a built-in Scheme.
• Invalid scheme name: {schemeName}
• Current Theme does not have a Scheme.
• Unexpected StartObject token when parsing Scheme: {reader.To
• After {propertyName}: Expected PropertyName but got another

AI-assisted analysis of tui-cs/Terminal.Gui@2e47b11478 (2026-08-13). Data as JSON: /api/errors/a8dea224257b3dd7. Report an issue: GitHub.