Determine sobject Type From Id Using SOAP API

best solution I've come up with so far is to use .describeGlobal() like this:

DescribeGlobalResult dgr = binding.describeGlobal();
DescribeGlobalSObjectResult dgsr = dgr.sobjects.FirstOrDefault(x =>
    string.IsNullOrEmpty(x.keyPrefix) ? false : id.StartsWith(x.keyPrefix));

    if (dgsr != null)
    {
        switch (dgsr.name)
        {
            case "custom1__c":
                ...
                break;
            case "custom2__c":
                ...
                break;
            case "custom3__c":
                ...
                break;
            default:
                ...
                break;
        }
    }