Compare two objects' properties to find differences?
Yes, with reflection - assuming each property type implements Equals appropriately. An alternative would be to use ReflectiveEquals recursively for all but some known types, but that gets tricky.
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;
}
The real problem: How to get the difference of two sets?
The fastest way I've found is to convert the sets to dictionaries first, then diff 'em. Here's a generic approach:
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;
}
Then you can do something like this:
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);
}
I know this is probably overkill, but here's my ObjectComparer class I use for this very purpose:
/// <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;
}
}
Sure you can with reflection. Here is the code to grab the properties off of a given type.
var info = typeof(SomeType).GetProperties();
If you can give more info on what you're comparing about the properties we can get together a basic diffing algorithmn. This code for intstance will diff on names
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);
}