Bandingkan properti dua benda untuk menemukan perbedaan?

Saya memiliki dua objek dengan tipe yang sama, dan saya ingin mengulang properti publik pada masing-masing objek dan memberi tahu pengguna tentang properti mana yang tidak cocok.

Apakah mungkin melakukan ini tanpa mengetahui properti apa yang dikandung objek?

Ya, dengan refleksi - dengan asumsi setiap tipe properti mengimplementasikan dengan Equalstepat. Alternatifnya adalah menggunakan ReflectiveEqualssecara rekursif untuk semua kecuali beberapa tipe yang diketahui, tetapi itu menjadi rumit.

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;
}

Tentu Anda bisa dengan refleksi. Berikut adalah kode untuk mengambil properti dari jenis yang diberikan.

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

Jika Anda dapat memberikan lebih banyak info tentang apa yang Anda bandingkan tentang properti, kami dapat mengumpulkan algoritma differing dasar. Kode intstance ini akan berbeda pada nama

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);
}

Saya tahu ini mungkin berlebihan, tapi inilah kelas ObjectComparer saya yang saya gunakan untuk tujuan ini:

/// <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;
    }
}

Masalah sebenarnya: Bagaimana cara mendapatkan perbedaan dua set?

Cara tercepat yang saya temukan adalah mengonversi set ke kamus terlebih dahulu, lalu perbeda. Berikut ini pendekatan umum:

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;
}

Maka Anda dapat melakukan sesuatu seperti ini:

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);
}

Iya. Gunakan Refleksi . Dengan Reflection, Anda dapat melakukan hal-hal seperti:

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

Dan kemudian Anda bisa menggunakan kelas PropertyInfo yang dihasilkan untuk membandingkan semua hal.

Membandingkan dua objek dengan tipe yang sama menggunakan LINQ dan Reflection. NB! Ini pada dasarnya adalah penulisan ulang solusi dari Jon Skeet, tetapi dengan sintaksis yang lebih ringkas dan modern. Itu juga harus menghasilkan IL sedikit lebih efektif.

Bunyinya seperti ini:

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 akan mencantumkan masing-masing properti dari jenis yang diberikan. Kemudian gunakan PropertyInfo.GetValue untuk memeriksa nilainya.

Seperti yang banyak disebutkan pendekatan rekursif, ini adalah fungsi yang Anda bisa berikan nama yang dicari dan properti untuk mulai dengan:

    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);
}