¿Comparar las propiedades de dos objetos para encontrar diferencias?

Tengo dos objetos del mismo tipo y quiero recorrer las propiedades públicas de cada uno de ellos y alertar al usuario sobre qué propiedades no coinciden.

¿Es posible hacer esto sin saber qué propiedades contiene el objeto?

Sí, con reflexión, suponiendo que cada tipo de propiedad se implemente Equalsadecuadamente. Una alternativa sería usar ReflectiveEqualsrecursivamente para todos menos algunos tipos conocidos, pero eso se vuelve complicado.

public bool ReflectiveEquals(object first, object second)
{
    if (first == null && second == null)
    {
        return true;
    }
    if (first == null || second == null)
    {
        return false;
    }
    Type firstType = first.GetType();
    if (second.GetType() != firstType)
    {
        return false; // Or throw an exception
    }
    // This will only use public properties. Is that enough?
    foreach (PropertyInfo propertyInfo in firstType.GetProperties())
    {
        if (propertyInfo.CanRead)
        {
            object firstValue = propertyInfo.GetValue(first, null);
            object secondValue = propertyInfo.GetValue(second, null);
            if (!object.Equals(firstValue, secondValue))
            {
                return false;
            }
        }
    }
    return true;
}

Claro que puedes con la reflexión. Aquí está el código para tomar las propiedades de un tipo dado.

var info = typeof(SomeType).GetProperties();

Si puede dar más información sobre lo que está comparando sobre las propiedades, podemos reunir un algoritmo básico diferente. Este código para intstance diferirá en los nombres

public bool AreDifferent(Type t1, Type t2) {
  var list1 = t1.GetProperties().OrderBy(x => x.Name).Select(x => x.Name);
  var list2 = t2.GetProperties().OrderBy(x => x.Name).Select(x => x.Name);
  return list1.SequenceEqual(list2);
}

Sé que esto probablemente sea excesivo, pero aquí está mi clase ObjectComparer que uso para este mismo propósito:

/// <summary>
/// Utility class for comparing objects.
/// </summary>
public static class ObjectComparer
{
    /// <summary>
    /// Compares the public properties of any 2 objects and determines if the properties of each
    /// all contain the same value.
    /// <para> 
    /// In cases where object1 and object2 are of different Types (both being derived from Type T) 
    /// we will cast both objects down to the base Type T to ensure the property comparison is only 
    /// completed on COMMON properties.
    /// (ex. Type T is Foo, object1 is GoodFoo and object2 is BadFoo -- both being inherited from Foo --
    /// both objects will be cast to Foo for comparison)
    /// </para>
    /// </summary>
    /// <typeparam name="T">Any class with public properties.</typeparam>
    /// <param name="object1">Object to compare to object2.</param>
    /// <param name="object2">Object to compare to object1.</param>
    /// <param name="propertyInfoList">A List of <see cref="PropertyInfo"/> objects that contain data on the properties
    /// from object1 that are not equal to the corresponding properties of object2.</param>
    /// <returns>A boolean value indicating whether or not the properties of each object match.</returns>
    public static bool GetDifferentProperties<T> ( T object1 , T object2 , out List<PropertyInfo> propertyInfoList )
        where T : class
    {
        return GetDifferentProperties<T>( object1 , object2 , null , out propertyInfoList );
    }

    /// <summary>
    /// Compares the public properties of any 2 objects and determines if the properties of each
    /// all contain the same value.
    /// <para> 
    /// In cases where object1 and object2 are of different Types (both being derived from Type T) 
    /// we will cast both objects down to the base Type T to ensure the property comparison is only 
    /// completed on COMMON properties.
    /// (ex. Type T is Foo, object1 is GoodFoo and object2 is BadFoo -- both being inherited from Foo --
    /// both objects will be cast to Foo for comparison)
    /// </para>
    /// </summary>
    /// <typeparam name="T">Any class with public properties.</typeparam>
    /// <param name="object1">Object to compare to object2.</param>
    /// <param name="object2">Object to compare to object1.</param>
    /// <param name="ignoredProperties">A list of <see cref="PropertyInfo"/> objects
    /// to ignore when completing the comparison.</param>
    /// <param name="propertyInfoList">A List of <see cref="PropertyInfo"/> objects that contain data on the properties
    /// from object1 that are not equal to the corresponding properties of object2.</param>
    /// <returns>A boolean value indicating whether or not the properties of each object match.</returns>
    public static bool GetDifferentProperties<T> ( T object1 , T object2 , List<PropertyInfo> ignoredProperties , out List<PropertyInfo> propertyInfoList )
        where T : class
    {
        propertyInfoList = new List<PropertyInfo>();

        // If either object is null, we can't compare anything
        if ( object1 == null || object2 == null )
        {
            return false;
        }

        Type object1Type = object1.GetType();
        Type object2Type = object2.GetType();

        // In cases where object1 and object2 are of different Types (both being derived from Type T) 
        // we will cast both objects down to the base Type T to ensure the property comparison is only 
        // completed on COMMON properties.
        // (ex. Type T is Foo, object1 is GoodFoo and object2 is BadFoo -- both being inherited from Foo --
        // both objects will be cast to Foo for comparison)
        if ( object1Type != object2Type )
        {
            object1Type = typeof ( T );
            object2Type = typeof ( T );
        }

        // Remove any properties to be ignored
        List<PropertyInfo> comparisonProps =
            RemoveProperties( object1Type.GetProperties() , ignoredProperties );

        foreach ( PropertyInfo object1Prop in comparisonProps )
        {
            Type propertyType = null;
            object object1PropValue = null;
            object object2PropValue = null;

            // Rule out an attempt to check against a property which requires
            // an index, such as one accessed via this[]
            if ( object1Prop.GetIndexParameters().GetLength( 0 ) == 0 )
            {
                // Get the value of each property
                object1PropValue = object1Prop.GetValue( object1 , null );
                object2PropValue = object2Type.GetProperty( object1Prop.Name ).GetValue( object2 , null );

                // As we are comparing 2 objects of the same type we know
                // that they both have the same properties, so grab the
                // first non-null value
                if ( object1PropValue != null )
                    propertyType = object1PropValue.GetType().GetInterface( "IComparable" );

                if ( propertyType == null )
                    if ( object2PropValue != null )
                        propertyType = object2PropValue.GetType().GetInterface( "IComparable" );
            }

            // If both objects have null values or were indexed properties, don't continue
            if ( propertyType != null )
            {
                // If one property value is null and the other is not null, 
                // they aren't equal; this is done here as a native CompareTo
                // won't work with a null value as the target
                if ( object1PropValue == null || object2PropValue == null )
                {
                    propertyInfoList.Add( object1Prop );
                }
                else
                {
                    // Use the native CompareTo method
                    MethodInfo nativeCompare = propertyType.GetMethod( "CompareTo" );

                    // Sanity Check:
                    // If we don't have a native CompareTo OR both values are null, we can't compare;
                    // hence, we can't confirm the values differ... just go to the next property
                    if ( nativeCompare != null )
                    {
                        // Return the native CompareTo result
                        bool equal = ( 0 == (int) ( nativeCompare.Invoke( object1PropValue , new object[] {object2PropValue} ) ) );

                        if ( !equal )
                        {
                            propertyInfoList.Add( object1Prop );
                        }
                    }
                }
            }
        }
        return propertyInfoList.Count == 0;
    }

    /// <summary>
    /// Compares the public properties of any 2 objects and determines if the properties of each
    /// all contain the same value.
    /// <para> 
    /// In cases where object1 and object2 are of different Types (both being derived from Type T) 
    /// we will cast both objects down to the base Type T to ensure the property comparison is only 
    /// completed on COMMON properties.
    /// (ex. Type T is Foo, object1 is GoodFoo and object2 is BadFoo -- both being inherited from Foo --
    /// both objects will be cast to Foo for comparison)
    /// </para>
    /// </summary>
    /// <typeparam name="T">Any class with public properties.</typeparam>
    /// <param name="object1">Object to compare to object2.</param>
    /// <param name="object2">Object to compare to object1.</param>
    /// <returns>A boolean value indicating whether or not the properties of each object match.</returns>
    public static bool HasSamePropertyValues<T> ( T object1 , T object2 )
        where T : class
    {
        return HasSamePropertyValues<T>( object1 , object2 , null );
    }

    /// <summary>
    /// Compares the public properties of any 2 objects and determines if the properties of each
    /// all contain the same value.
    /// <para> 
    /// In cases where object1 and object2 are of different Types (both being derived from Type T) 
    /// we will cast both objects down to the base Type T to ensure the property comparison is only 
    /// completed on COMMON properties.
    /// (ex. Type T is Foo, object1 is GoodFoo and object2 is BadFoo -- both being inherited from Foo --
    /// both objects will be cast to Foo for comparison)
    /// </para>
    /// </summary>
    /// <typeparam name="T">Any class with public properties.</typeparam>
    /// <param name="object1">Object to compare to object2.</param>
    /// <param name="object2">Object to compare to object1.</param>
    /// <param name="ignoredProperties">A list of <see cref="PropertyInfo"/> objects
    /// to ignore when completing the comparison.</param>
    /// <returns>A boolean value indicating whether or not the properties of each object match.</returns>
    public static bool HasSamePropertyValues<T> ( T object1 , T object2 , List<PropertyInfo> ignoredProperties )
        where T : class
    {

        // If either object is null, we can't compare anything
        if ( object1 == null || object2 == null )
        {
            return false;
        }

        Type object1Type = object1.GetType();
        Type object2Type = object2.GetType();

        // In cases where object1 and object2 are of different Types (both being derived from Type T) 
        // we will cast both objects down to the base Type T to ensure the property comparison is only 
        // completed on COMMON properties.
        // (ex. Type T is Foo, object1 is GoodFoo and object2 is BadFoo -- both being inherited from Foo --
        // both objects will be cast to Foo for comparison)
        if ( object1Type != object2Type )
        {
            object1Type = typeof ( T );
            object2Type = typeof ( T );
        }

        // Remove any properties to be ignored
        List<PropertyInfo> comparisonProps =
            RemoveProperties( object1Type.GetProperties() , ignoredProperties );

        foreach ( PropertyInfo object1Prop in comparisonProps )
        {
            Type propertyType = null;
            object object1PropValue = null;
            object object2PropValue = null;

            // Rule out an attempt to check against a property which requires
            // an index, such as one accessed via this[]
            if ( object1Prop.GetIndexParameters().GetLength( 0 ) == 0 )
            {
                // Get the value of each property
                object1PropValue = object1Prop.GetValue( object1 , null );
                object2PropValue = object2Type.GetProperty( object1Prop.Name ).GetValue( object2 , null );

                // As we are comparing 2 objects of the same type we know
                // that they both have the same properties, so grab the
                // first non-null value
                if ( object1PropValue != null )
                    propertyType = object1PropValue.GetType().GetInterface( "IComparable" );

                if ( propertyType == null )
                    if ( object2PropValue != null )
                        propertyType = object2PropValue.GetType().GetInterface( "IComparable" );
            }

            // If both objects have null values or were indexed properties, don't continue
            if ( propertyType != null )
            {
                // If one property value is null and the other is not null, 
                // they aren't equal; this is done here as a native CompareTo
                // won't work with a null value as the target
                if ( object1PropValue == null || object2PropValue == null )
                {
                    return false;
                }

                // Use the native CompareTo method
                MethodInfo nativeCompare = propertyType.GetMethod( "CompareTo" );

                // Sanity Check:
                // If we don't have a native CompareTo OR both values are null, we can't compare;
                // hence, we can't confirm the values differ... just go to the next property
                if ( nativeCompare != null )
                {
                    // Return the native CompareTo result
                    bool equal = ( 0 == (int) ( nativeCompare.Invoke( object1PropValue , new object[] {object2PropValue} ) ) );

                    if ( !equal )
                    {
                        return false;
                    }
                }
            }
        }
        return true;
    }

    /// <summary>
    /// Removes any <see cref="PropertyInfo"/> object in the supplied List of 
    /// properties from the supplied Array of properties.
    /// </summary>
    /// <param name="allProperties">Array containing master list of 
    /// <see cref="PropertyInfo"/> objects.</param>
    /// <param name="propertiesToRemove">List of <see cref="PropertyInfo"/> objects to
    /// remove from the supplied array of properties.</param>
    /// <returns>A List of <see cref="PropertyInfo"/> objects.</returns>
    private static List<PropertyInfo> RemoveProperties (
        IEnumerable<PropertyInfo> allProperties , IEnumerable<PropertyInfo> propertiesToRemove )
    {
        List<PropertyInfo> innerPropertyList = new List<PropertyInfo>();

        // Add all properties to a list for easy manipulation
        foreach ( PropertyInfo prop in allProperties )
        {
            innerPropertyList.Add( prop );
        }

        // Sanity check
        if ( propertiesToRemove != null )
        {
            // Iterate through the properties to ignore and remove them from the list of 
            // all properties, if they exist
            foreach ( PropertyInfo ignoredProp in propertiesToRemove )
            {
                if ( innerPropertyList.Contains( ignoredProp ) )
                {
                    innerPropertyList.Remove( ignoredProp );
                }
            }
        }

        return innerPropertyList;
    }
}

El verdadero problema: ¿Cómo obtener la diferencia de dos conjuntos?

La forma más rápida que he encontrado es convertir primero los conjuntos a diccionarios, luego difuminarlos. Aquí hay un enfoque genérico:

static IEnumerable<T> DictionaryDiff<K, T>(Dictionary<K, T> d1, Dictionary<K, T> d2)
{
    return from x in d1 where !d2.ContainsKey(x.Key) select x.Value;
}

Entonces puedes hacer algo como esto:

static public IEnumerable<PropertyInfo> PropertyDiff(Type t1, Type t2)
{
    var d1 = t1.GetProperties().ToDictionary(x => x.Name);
    var d2 = t2.GetProperties().ToDictionary(x => x.Name);
    return DictionaryDiff(d1, d2);
}

Si. Utiliza la reflexión . Con Reflection, puedes hacer cosas como:

//given object of some type
object myObjectFromSomewhere;
Type myObjOriginalType = myObjectFromSomewhere.GetType();
PropertyInfo[] myProps = myObjOriginalType.GetProperties();

Y luego puede usar las clases PropertyInfo resultantes para comparar todo tipo de cosas.

Comparar dos objetos del mismo tipo usando LINQ y Reflection. ¡NÓTESE BIEN! Esto es básicamente una reescritura de la solución de Jon Skeet, pero con una sintaxis más compacta y moderna. También debería generar un poco más de IL efectiva.

Es algo parecido a esto:

public bool ReflectiveEquals(LocalHdTicket serverTicket, LocalHdTicket localTicket)
  {
     if (serverTicket == null && localTicket == null) return true;
     if (serverTicket == null || localTicket == null) return false;

     var firstType = serverTicket.GetType();
     // Handle type mismatch anyway you please:
     if(localTicket.GetType() != firstType) throw new Exception("Trying to compare two different object types!");

     return !(from propertyInfo in firstType.GetProperties() 
              where propertyInfo.CanRead 
              let serverValue = propertyInfo.GetValue(serverTicket, null) 
              let localValue = propertyInfo.GetValue(localTicket, null) 
              where !Equals(serverValue, localValue) 
              select serverValue).Any();
  }

Type.GetProperties enumerará cada una de las propiedades de un tipo determinado. Luego use PropertyInfo.GetValue para verificar los valores.

Como muchos mencionaron el enfoque recursivo, esta es la función que puede pasar el nombre buscado y la propiedad para comenzar:

    public static void loopAttributes(PropertyInfo prop, string targetAttribute, object tempObject)
    {
        foreach (PropertyInfo nestedProp in prop.PropertyType.GetProperties())
        {
            if(nestedProp.Name == targetAttribute)
            {
                //found the matching attribute
            }
            loopAttributes(nestedProp, targetAttribute, prop.GetValue(tempObject);
        }
    }

//in the main function
foreach (PropertyInfo prop in rootObject.GetType().GetProperties())
{
    loopAttributes(prop, targetAttribute, rootObject);
}