Custom Admin controller not working

Question

I am developing a module & created admin controller but working on url

mymagentosite.com/index.php/admin/transaction/index

show error:There has been an error processing your request
error in the file is

a:5:{i:0;s:51:"Controller file was loaded but class does not exist";i:1;s:1106:".../magento/app/code/core/Mage/Core/Controller/Varien/Router/Standard.php(326): Mage::exception('Mage_Core', 'Controller file...')

code is here Namespace/Modulename/etc/config.xml

<admin>
        <routers>
            <adminhtml>
                <args>
                    <modules>
                        <modulename before="Mage_Adminhtml">Namesapce_Modulename_Adminhtml</modulename>
                    </modules>
                </args>
            </adminhtml>
        </routers>
    </admin>

Namespace/Modulename/controller/Adminhtml/TransationController.php

<?php
class Namespace_Modulename_Adminhtml_TransationController extends Mage_Adminhtml_Controller_Action
{

    public function indexAction()
    {
        echo "string";
    }
}

Answer 1

The error message is pretty clear about it:

Controller file was loaded but class does not exist

So the controller file has been loaded but the class name is wrong. Class name and file name in your question seem to match, but I noticed that TransationController probably should read TransactionController ("C" is missing).

Double check that file name and class name match

Answer 2

fschmengler's answer is correct. There is another type in config.xml with a and p swapped in Namespace: Namesapce_Modulename_Adminhtml

Should be Namespace_Modulename_Adminhtml.