Adding custom properties

Context: Custom exceptions can include additional properties that carry contextual information about the error. For example, a ValidationException might have a PropertyName and InvalidValue. These properties help the caller understand and handle the error without parsing the message string. They should be serializable as well.

Usage Example

using System;
using System.Runtime.Serialization;

[Serializable]
public class ValidationException : Exception
{
    public string PropertyName { get; }
    public object InvalidValue { get; }

    public ValidationException() { }

    public ValidationException(string message) : base(message) { }

    public ValidationException(string message, Exception inner) : base(message, inner) { }

    public ValidationException(string propertyName, object invalidValue, string message)
        : base(message)
    {
        PropertyName = propertyName;
        InvalidValue = invalidValue;
    }

    protected ValidationException(SerializationInfo info, StreamingContext context)
        : base(info, context)
    {
        PropertyName = info.GetString("PropertyName");
        InvalidValue = info.GetValue("InvalidValue", typeof(object));
    }

    public override void GetObjectData(SerializationInfo info, StreamingContext context)
    {
        base.GetObjectData(info, context);
        info.AddValue("PropertyName", PropertyName);
        info.AddValue("InvalidValue", InvalidValue);
    }
}

class Program
{
    static void Main()
    {
        try
        {
            throw new ValidationException("Age", -5, "Age cannot be negative.");
        }
        catch (ValidationException ex)
        {
            Console.WriteLine($"Validation failed for {ex.PropertyName}: {ex.Message}");
        }
    }
}

Output console

dotnet run
Validation failed for Age: Age cannot be negative.

Important notes

Override GetObjectData for custom serialization.
Use read‑only properties for immutable exception data.
Avoid storing large objects in exception properties.

Real-world usage example

API client – A ApiException with StatusCode and ResponseBody properties to help debugging.
See .NET docs on custom exception properties.

Adding custom properties

Usage Example

Output console

Important notes

Real-world usage example

Related sections