tui-cs/Terminal.Gui · error · InvalidOperationException

: 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.

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

• Current Theme does not have a Scheme.
• Invalid scheme name
• : Cannot remove a built-in Scheme.
• After : Expected Attribute but got when parsing Scheme.
• After : Expected PropertyName but got another token when…

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

Appendix: 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]!;
    }

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