OrchardCMS/OrchardCore · error · InvalidCastException

Cannot convert to Guid

Error message

Cannot convert {value} to Guid

What it means

The explicit operator Guid on JsonDynamicValue converts via GetValue<Guid>() and throws InvalidCastException when the result is null or the JSON token is not a parseable GUID string. It fails fast with a descriptive message; use the (Guid?) operator for non-throwing access.

Solutions

1. Confirm the JSON value is a valid GUID string (32 hex digits / with-dashes format) before casting
2. Use the nullable cast (Guid?) and treat null as 'no identifier'
3. Validate with Guid.TryParse(value.ToString(), out var g) first, especially if IDs may be non-GUID strings
4. Null-check the wrapper before casting

Example fix

// before
var id = (Guid)jsonDynamicValue["ContentItemId"];
// after
var id = (Guid?)jsonDynamicValue["ContentItemId"] ?? Guid.NewGuid();

if (jsonDynamicValue is null) throw new InvalidOperationException("null wrapper");
var raw = jsonDynamicValue.ToString();
if (!Guid.TryParse(raw, out _))
    throw new InvalidOperationException($"'{raw}' is not a GUID");
var g = (Guid)jsonDynamicValue;

static bool TryGetGuid(JsonDynamicValue v, out Guid value)
{
    value = default;
    if (v is null) return false;
    var g = (Guid?)v;
    if (g is null) return false;
    value = g.Value;
    return true;
}

Guid id;
try
{
    id = (Guid)jsonDynamicValue["ContentItemId"];
}
catch (InvalidCastException ex)
{
    id = Guid.Empty;
}

When it happens

Trigger: Executing `(Guid)jsonDynamicValue` where the wrapper/_jsonValue is null or the token is a string not in a GUID-parseable format, a number, boolean, object, or array.

Common situations: Identifier fields (content item IDs, relation keys) in JSON that are null, empty, or stored in a non-GUID format (e.g. integers or short slugs); data migrated from another system that used different ID formats.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Cannot convert to DateTime
• Cannot convert to DateTimeOffset
• Cannot convert to Decimal
• Cannot convert to Double
• Cannot convert to

AI-assisted analysis of OrchardCMS/OrchardCore@4306c0717f (2026-09-13). Data as JSON: /api/errors/187ca3e6728e2295. Report an issue: GitHub.

Appendix: source

Thrown at src/OrchardCore/OrchardCore.Abstractions/Json/Dynamic/JsonDynamicValue.cs:351

    {
        return value?._jsonValue?.GetValue<decimal?>();
    }

    public static explicit operator double(JsonDynamicValue value)
    {
        return value?._jsonValue?.GetValue<double>()
            ?? throw new InvalidCastException($"Cannot convert {value} to Double");
    }

    public static explicit operator double?(JsonDynamicValue value)
    {
        return value?._jsonValue?.GetValue<double?>();
    }

    public static explicit operator Guid(JsonDynamicValue value)
    {
        return value?._jsonValue?.GetValue<Guid>()
            ?? throw new InvalidCastException($"Cannot convert {value} to Guid");
    }

    public static explicit operator Guid?(JsonDynamicValue value)
    {
        return value?._jsonValue?.GetValue<Guid?>();
    }

    public static explicit operator short(JsonDynamicValue value)
    {
        return value?._jsonValue?.GetValue<short>()
            ?? throw new InvalidCastException($"Cannot convert {value} to Int16");
    }

    public static explicit operator short?(JsonDynamicValue value)
    {
        return value?._jsonValue?.GetValue<short?>();
    }

View on GitHub (pinned to 4306c0717f)