elsa-workflows/elsa-core · error · Exception

Failed to convert an object of type

Error message

Failed to convert an object of type {sourceType} to {underlyingTargetType}

What it means

ObjectConverter.ConvertTo uses Convert.ChangeType for scalar conversions and rethrows InvalidCastException as a generic Exception naming the source and target types. It means the source value cannot be losslessly converted to the requested primitive type.

Solutions

1. Ensure the source value is convertible (e.g. int.TryParse first) to the target type
2. Correct the input value or the expected property type
3. Catch the exception and fall back to a default value

Example fix

// before
var n = ObjectConverter.ConvertTo<int>("abc");
// after
var n = int.TryParse("abc", out var v) ? v : 0;

if (value is string s && !double.TryParse(s, NumberStyles.Any, CultureInfo.InvariantCulture, out _))
    throw new FormatException($"'{s}' is not numeric");

try { n = ObjectConverter.ConvertTo<int>(value); } catch (Exception) { n = 0; }

When it happens

Trigger: Converting e.g. a string "abc" to int, a DateTime to int, or a complex object to a numeric type via ConvertTo<T>.

Common situations: Workflow variable test values or inputs with wrong types compared to property types; culture/number-format issues with decimal strings; schema changes between workflow definition versions.

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 deserialize to .
• Failed to deserialize
• Invalid value type.
• Invalid target type.
• Value cannot be null. (Parameter 'type')

AI-assisted analysis of elsa-workflows/elsa-core@fe9217bdfa (2026-09-13). Data as JSON: /api/errors/54bc75b21e24fede. Report an issue: GitHub.

Appendix: source

Thrown at src/clients/Elsa.Api.Client/Extensions/ObjectConverter.cs:185

                    foreach (var item in enumerable)
                    {
                        var convertedItem = ConvertTo(item, desiredCollectionItemType);
                        collection.Add(convertedItem);
                    }

                    return collection;
                }
            }
        }

        try
        {
            return Convert.ChangeType(value, underlyingTargetType, CultureInfo.InvariantCulture);
        }
        catch (InvalidCastException)
        {
            throw new Exception($"Failed to convert an object of type {sourceType} to {underlyingTargetType}");
        }
    }

    /// <summary>
    /// Returns true if the specified type is date-like type, false otherwise.
    /// </summary>
    private static bool IsDateType(Type type)
    {
        var dateTypes = new[]
        {
            typeof(DateTime),
            typeof(DateTimeOffset)
        };

        return dateTypes.Contains(type);
    }

    /// <summary>

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