OrchardCMS/OrchardCore · error · InvalidCastException

Cannot convert to Decimal

Error message

Cannot convert {value} to Decimal

What it means

The explicit operator decimal on JsonDynamicValue converts the wrapped JSON value with GetValue<decimal>() and throws InvalidCastException when conversion yields null or the JSON token is not numeric-decimal-compatible. It provides a descriptive message rather than letting the JSON library surface a vaguer failure.

Solutions

1. Confirm the JSON token is a JSON number (or an invariant numeric string accepted by the JSON parser)
2. Use the nullable cast (decimal?) and coalesce/handle null
3. Convert explicitly with decimal.TryParse(value.ToString(), NumberStyles.Any, CultureInfo.InvariantCulture, out var d) when values may be numeric strings
4. Null-check the wrapper before casting

Example fix

// before
var price = (decimal)jsonDynamicValue["Price"];
// after
var price = (decimal?)jsonDynamicValue["Price"] ?? 0m;

if (jsonDynamicValue is null) throw new InvalidOperationException("null wrapper");
var raw = jsonDynamicValue.ToString();
if (!decimal.TryParse(raw, NumberStyles.Number, CultureInfo.InvariantCulture, out _))
    throw new InvalidOperationException($"'{raw}' is not a decimal");
var d = (decimal)jsonDynamicValue;

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

decimal amount;
try
{
    amount = (decimal)jsonDynamicValue["Price"];
}
catch (InvalidCastException ex)
{
    amount = 0m;
}

When it happens

Trigger: Executing `(decimal)jsonDynamicValue` where the wrapper/_jsonValue is null, or the token is a non-numeric string, boolean, object, or array (numbers stored as strings also fail).

Common situations: Money/quantity fields in JSON content that are null, empty strings, or strings like "12,50" with locale-specific formatting; columns that changed from number to string in stored JSON; dynamic query results.

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 Double
• Cannot convert to Guid
• Cannot convert to

AI-assisted analysis of OrchardCMS/OrchardCore@4306c0717f (2026-09-13). Data as JSON: /api/errors/2f0083c1bb25a667. Report an issue: GitHub.

Appendix: source

Thrown at src/OrchardCore/OrchardCore.Abstractions/Json/Dynamic/JsonDynamicValue.cs:329

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

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

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

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

    public static explicit operator decimal?(JsonDynamicValue value)
    {
        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?>();
    }

View on GitHub (pinned to 4306c0717f)