microsoft/aspire · error · JsonException

Invalid boolean value

Error message

Invalid boolean value: '{value}'. Expected 'true' or 'false'.

What it means

FlexibleBooleanConverter.Read parses a JSON string token as a bool via bool.TryParse; if the token cannot be parsed, the custom converter throws JsonException to fail deserialization of a flexible boolean setting. It exists so config values like "True"/"false" strings deserialize, but anything unparseable is rejected.

Solutions

1. Open the JSON config file and replace the offending string with exactly 'true' or 'false' (quoted strings are accepted, casing-insensitively).
2. If the value comes from an environment variable or script, fix the upstream source to emit 'true'/'false'.
3. If you need looser parsing (yes/1/on), extend ParseString to accept those tokens before throwing.

Example fix

// before
"features": { "experimentalFeature": "yes" }
// after
"features": { "experimentalFeature": "true" }

var trimmed = raw?.Trim();
if (!bool.TryParse(trimmed, out _))
    throw new FormatException($"Value '{raw}' must be 'true' or 'false'.");

static bool IsValidBooleanString(string? s) => bool.TryParse(s, out _);

try
{
    var value = JsonSerializer.Deserialize<MyConfig>(json, options);
}
catch (JsonException ex) when (ex.Message.Contains("Invalid boolean value"))
{
    logger.LogError(ex, "Config contains a non-boolean string where true/false expected.");
}

When it happens

Trigger: Deserializing configuration JSON where a property bound through this converter contains a string token other than (case-insensitive per TryParse) 'true'/'false'/'True'/'False' — e.g. "yes", "1", "on", or an empty string.

Common situations: Hand-edited aspire config files where the user wrote 'yes' or '1' instead of 'true'; config values interpolated from environment variables that contain unexpected text; older docs or other tools writing truthy strings.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• Cannot convert string
• Expected StartObject, got
• Cannot convert to boolean for key
• Error deserializing GenAI message content. Error description
• Expected a non-empty Kubernetes MicroTime value.

AI-assisted analysis of microsoft/aspire@25830f84bd (2026-09-16). Data as JSON: /api/errors/089fa2ba304a1c84. Report an issue: GitHub.

Appendix: source

Thrown at src/Aspire.Cli/Configuration/FlexibleBooleanConverter.cs:35

    public override bool Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        return reader.TokenType switch
        {
            JsonTokenType.True => true,
            JsonTokenType.False => false,
            JsonTokenType.String => ParseString(reader.GetString()),
            _ => throw new JsonException($"Unexpected token parsing boolean. Token: {reader.TokenType}")
        };
    }

    private static bool ParseString(string? value)
    {
        if (bool.TryParse(value, out var result))
        {
            return result;
        }

        throw new JsonException($"Invalid boolean value: '{value}'. Expected 'true' or 'false'.");
    }

    public override void Write(Utf8JsonWriter writer, bool value, JsonSerializerOptions options)
    {
        writer.WriteBooleanValue(value);
    }
}

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