Comparing two dictionaries for equal data in c#?

Question

I have two dictionaries containing a string key and then an object. The object contains five fields. Is there an elegant way to ensure both dictionaries first contain the same keys and then if this is correct, contain the same five fields per object?

Would the two dictionaries have the same in-built hashcode or something?

EDIT, doesn't appear to be working for the following code:

Dictionary<string, MyClass> test1 = new Dictionary<string, MyClass>();
Dictionary<string, MyClass> test2 = new Dictionary<string, MyClass>();

MyClass i = new MyClass("", "", 1, 1, 1, 1);
MyClass j = new MyClass("", "", 1, 1, 1, 1);

test1.Add("1", i);
test2.Add("1", j);

bool equal = test1.OrderBy(r => r.Key).SequenceEqual(test2.OrderBy(r => r.Key));

class MyClass
{
    private string a;
    private string b;
    private long? c;
    private decimal d;
    private decimal e;
    private decimal f;

    public MyClass(string aa, string bb, long? cc, decimal dd, decimal ee, decimal ff)
    {
        a= aa;
        b= bb;
        c= cc;
        d= dd;
        e= ee;
        f= ff;
    }

this returns false?

Answer 1

First you have to override Equals and GetHashCode method in your class, otherwise comparison will be performed on references instead of actual values. (The code to override Equals and GetHashCode is provided at the end), after that you can use:

var result = (dic1 == dic2) || //Reference comparison (if both points to same object)
             (dic1.Count == dic2.Count && !dic1.Except(dic2).Any());

Since the order in which items in Dictionary are returned is undefined, you can not rely on Dictionary.SequenceEqual (without OrderBy).

You can try:

Dictionary<string, object> dic1 = new Dictionary<string, object>();
Dictionary<string, object> dic2 = new Dictionary<string, object>();
dic1.Add("Key1", new { Name = "abc", Number = "123", Address = "def", Loc = "xyz" });
dic1.Add("Key2", new { Name = "DEF", Number = "123", Address = "def", Loc = "xyz" });
dic1.Add("Key3", new { Name = "GHI", Number = "123", Address = "def", Loc = "xyz" });
dic1.Add("Key4", new { Name = "JKL", Number = "123", Address = "def", Loc = "xyz" });

dic2.Add("Key1",new { Name = "abc",Number=  "123", Address= "def", Loc="xyz"});
dic2.Add("Key2", new { Name = "DEF", Number = "123", Address = "def", Loc = "xyz" });
dic2.Add("Key3", new { Name = "GHI", Number = "123", Address = "def", Loc = "xyz" });
dic2.Add("Key4", new { Name = "JKL", Number = "123", Address = "def", Loc = "xyz" });


bool result = dic1.SequenceEqual(dic2); //Do not use that

Most of the time the above will return true, but one can't really rely on that due to unordered nature of Dictionary.

Since SequenceEqual will compare the order as well, therefore relying on only SequenceEqual could be wrong. You have to use OrderBy to order both dictionaries and then use SequenceEqual like:

bool result2 = dic1.OrderBy(r=>r.Key).SequenceEqual(dic2.OrderBy(r=>r.Key));

But that will involve multiple iterations, once for ordering and the other for comparing each element using SequenceEqual.

Code for overriding Equals and GetHashCode

private class MyClass
{
    private string a;
    private string b;
    private long? c;
    private decimal d;
    private decimal e;
    private decimal f;

    public MyClass(string aa, string bb, long? cc, decimal dd, decimal ee, decimal ff)
    {
        a = aa;
        b = bb;
        c = cc;
        d = dd;
        e = ee;
        f = ff;
    }

    protected bool Equals(MyClass other)
    {
        return string.Equals(a, other.a) && string.Equals(b, other.b) && c == other.c && e == other.e && d == other.d && f == other.f;
    }

    public override bool Equals(object obj)
    {
        if (ReferenceEquals(null, obj)) return false;
        if (ReferenceEquals(this, obj)) return true;
        if (obj.GetType() != this.GetType()) return false;
        return Equals((MyClass)obj);
    }

    public override int GetHashCode()
    {
        unchecked
        {
            var hashCode = (a != null ? a.GetHashCode() : 0);
            hashCode = (hashCode * 397) ^ (b != null ? b.GetHashCode() : 0);
            hashCode = (hashCode * 397) ^ c.GetHashCode();
            hashCode = (hashCode * 397) ^ e.GetHashCode();
            hashCode = (hashCode * 397) ^ d.GetHashCode();
            hashCode = (hashCode * 397) ^ f.GetHashCode();
            return hashCode;
        }
    }
}

You may also see: Correct way to override Equals() and GetHashCode()