Get variable name referring the object in C#

I am not sure that I understand your question, but I interpret it this way:

User someUser = new User();
User anotherVariable = someUser;

Now you want to find someUser using the object referenced by anotherVariable (which is the user object originally assigned to someUser). If that is the question, the answer is no, that is not possible (AFAIK).

You can do this by using reflection to walk the object hierarchy and look for fields that reference the object you're looking for. Here's a function I use to accomplish this. You must provide a root object for its search.

This could probably be improved upon if you can look at the root stack frame and walk the local variables in there, but for my purposes, the app usually knows the rootmost object that it cares about.

// Spew all references to obj throughout the object hierarchy.
public static void FindReferences( object appRootObject, object obj )
{
    Stack<ReferencePath> stack = new Stack<ReferencePath>();
    FindReferences_R( stack, appRootObject, obj );
}

struct ReferencePath
{
    public ReferencePath( object parentObj, FieldInfo parentField )
    {
        m_ParentObject = parentObj;
        m_ParentField = parentField;
    }

    public object m_ParentObject;
    public FieldInfo m_ParentField;
}

static void PrintReferencePath( Stack< ReferencePath > stack )
{
    string s = "RootObject";
    foreach ( ReferencePath path in stack.ToArray().Reverse() )
    {
        s += "." + path.m_ParentField.Name;
    }
    System.Console.WriteLine( s );
}

static bool StackContainsParent( Stack< ReferencePath > stack, object obj )
{
    foreach ( ReferencePath path in stack )
    {
        if ( path.m_ParentObject == obj )
            return true;
    }

    return false;
}

static void FindReferences_R( Stack< ReferencePath > stack, object curParent, object obj )
{
    Type parentType = curParent.GetType();

    foreach ( MemberInfo memberInfo in parentType.GetMembers( BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance ) )
    {
        FieldInfo fieldInfo = memberInfo as FieldInfo;
        if ( fieldInfo == null )
            continue;

        Type fieldType = fieldInfo.FieldType;
        if ( !fieldType.IsClass )
            continue;

        object value = fieldInfo.GetValue( curParent );
        if ( value == null )
            continue;

        stack.Push( new ReferencePath( curParent, fieldInfo ) );
        if ( value == obj )
        {
            PrintReferencePath( stack );
        }

        // Recurse, but don't recurse forever.
        if ( !StackContainsParent( stack, value ) )
        {
            FindReferences_R( stack, value, obj );
        }

        stack.Pop();
    }
}