Need to send a hidden input value to mvc controller using angularjs

Have you tried with query string ?

var pID=$scope.ProjectId
$http({ method: 'GET', url: '/User/GetProjectsList?ProjectID='+pID}).
    success(function (data, status, headers, config) {         
        $scope.workflow = [];

        $scope.Projects = data;

    }).
 error(function (data, status, headers, config) {
     alert('error');
 })

;

I hope this helped you ;)

 app.controller("myCtrl", function($scope) {
   $scope.formDetails = {};
   $scope.sendToApi = function(){
       var model = {
          id: $scope.formDetails.id //this is my hidden input
          name: $scope.formDetails.name,
       }
       //and then send your model to API
   }
})

It seems like AngularJS does not take in consideration hidden input when submitting forms, check this issue for more details. But you can get your value in 2 ways:

1. classic way:

remove ng-model since has no sens with hidden type as explained above and add id:

<input id="project_id" type="hidden" value="{{ProjectsObj.IDWorkflow}}"/>

in Javascript side you simply do:

var project_id = document.getElementById('45').value;

2. AngularJS way

since Angular ignores hidden elements, you can replace it with type=text and display:none:

<input type="text" name="project_id" ng-model="projectID" style="display: none;"/>

and your javascript side using two way data-binding you can acces your ng-model variable:

var project_id = $scope.projectID;

 @Html.HiddenFor(m => m.ProjectId)

You Can Simply Pass Hidden Value To Controller From View By using model value like above syntax.