Solution 1:

This guy always has the right answer: https://github.com/angular/material/issues/455#issuecomment-59889129

In short:

$mdDialog.show({
            locals:{dataToPass: $scope.parentScopeData},                
            clickOutsideToClose: true,                
            controllerAs: 'ctrl',                
            templateUrl: 'quotation/edit/',//+edit_id,
            controller: mdDialogCtrl,
        });

var mdDialogCtrl = function ($scope, dataToPass) { 
    $scope.mdDialogData = dataToPass  
}

Pass the variable using the locals attribute in the passing object. These values will be injected into the controller not the $scope. Also passing the entire $scope of the parent might not be such a good idea as it defeats the isolated scope paradigm.

Solution 2:

HTML

<md-button ng-click='vmInter.showDialog($event,_dataToPass)'>
<i class="fa fa-custom-edit" aria-hidden="true"></i>
</md-button>

Js

    function _showSiebelDialog(event,_dataToPass) {

        $mdDialog.show({
                locals:{dataToPass: _dataToPass}, //here where we pass our data
                controller: _DialogController,
                controllerAs: 'vd',
                templateUrl: 'contentComponents/prepare/views/Dialog.tmpl.html',
                parent: angular.element(document.body),
                targetEvent: event,
                clickOutsideToClose: true

            })
            .then(
                function(answer) {},
                function() {

                }
            );
    };

function _DialogController($scope, $mdDialog,dataToPass) {
console.log('>>>>>>> '+dataToPass);
}

Solution 3:

$scope.showPrompt = function(yourObject) {
$mdDialog.show({
    templateUrl: 'app/views/your-dialog.tpl.html',
    locals: {
        callback: $scope.yourFunction // create the function  $scope.yourFunction = function (yourVariable) {
    },
    controller:  function ($scope, $mdDialog, callback) {
        $scope.dialog.title = 'Your title';
        $scope.dialog.abort = function () {
            $mdDialog.hide();
        };
        $scope.dialog.hide = function () {

            if ($scope.Dialog.$valid){
                $mdDialog.hide();
                callback($scope.yourReturnValue, likes the return of input field);
            }
        };
    },
    controllerAs: 'dialog',
    bindToController: true,
    clickOutsideToClose: true,
    escapeToClose: true
});

};