在序列化中将一种对象与另一种对象进行比较

Question

I have some classes with Equals and GetHashCode methods overriden. Like this:

    // LevelData.cs
    public override bool Equals (object obj)
    {
        return id == ((LevelData)obj).id;
    }

When I try to save an object (via serialization), a type of object is compared to another inside a Equals. I dont understand how. This is the erro i get:

InvalidCastException: Cannot cast from source type to destination type.
LevelData.Equals (System.Object obj) (at Assets/Scripts/Map/LevelData.cs:50)
System.Collections.Hashtable.KeyEquals (System.Object item, System.Object key) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Collections/Hashtable.cs:679)
System.Collections.Hashtable.Find (System.Object key) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Collections/Hashtable.cs:730)
System.Collections.Hashtable.Contains (System.Object key) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Collections/Hashtable.cs:494)
System.Runtime.Serialization.SerializationObjectManager.RegisterObject (System.Object obj) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Runtime.Serialization/SerializationObjectManager.cs:50)
System.Runtime.Serialization.Formatters.Binary.ObjectWriter.GetObjectData (System.Object obj, System.Runtime.Serialization.Formatters.Binary.TypeMetadata& metadata, System.Object& data) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/ObjectWriter.cs:389)
System.Runtime.Serialization.Formatters.Binary.ObjectWriter.WriteObject (System.IO.BinaryWriter writer, Int64 id, System.Object obj) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/ObjectWriter.cs:306)
System.Runtime.Serialization.Formatters.Binary.ObjectWriter.WriteObjectInstance (System.IO.BinaryWriter writer, System.Object obj, Boolean isValueObject) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/ObjectWriter.cs:293)
System.Runtime.Serialization.Formatters.Binary.ObjectWriter.WriteQueuedObjects (System.IO.BinaryWriter writer) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/ObjectWriter.cs:271)
System.Runtime.Serialization.Formatters.Binary.ObjectWriter.WriteObjectGraph (System.IO.BinaryWriter writer, System.Object obj, System.Runtime.Remoting.Messaging.Header[] headers) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/ObjectWriter.cs:256)
System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize (System.IO.Stream serializationStream, System.Object graph, System.Runtime.Remoting.Messaging.Header[] headers) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/BinaryFormatter.cs:232)
System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize (System.IO.Stream serializationStream, System.Object graph) (at /Users/builduser/buildslave/monoAndRuntimeClassLibs/build/mcs/class/corlib/System.Runtime.Serialization.Formatters.Binary/BinaryFormatter.cs:211)
PlayerProfile.Save () (at Assets/Scripts/PlayerProfile.cs:95)

Answer 1

As a guess, objects of type LevelData are compared to the objects of another types during serialization. Try to check the Type of the obj before casting:

public override bool Equals (object obj)
{
    return obj is LevelData ? id == ((LevelData)obj).id : false;
}