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ASP.NET Core MVC: How to load a partial view

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1 Introduction

This article is going to describe how to show a partial view when a button clicks. The sample application shows the search form with all the students records. When search button clicks, it's going to only render student list from students partial view, search form is not getting rendered again. This is a small example of how to load a partial view for a user action using ajax request.You can use this as a sample and handle a more complex scenario.

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2 Background

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3 Create ASP.NET Core project

Let's create a ASP.NET Core project from Visual Studio, Let's check what is the Visual Studio version in your development environment, if it's not up to date, will update it to the latest version.
Open Visual Studio, from menu go to Help -> Check for Updates It will show Visual Studio is up to date and latest version is *Visual Studio 2017 - 15.8.1


*
Let's create new solution from Visual Studio, Click on File -> New -> Project, you will get a window as shown below, click on Visual C# -> .NET Core and select ASP.NET Core Web Application from available templates. You can give a name and a location for the solution

You can select a project template from below screen, let's go with Web Application (Model - View - Controller) since we are going to create a solution with MVC pattern, In this sample we are creating the project with the latest .NET Core version, *ASP.NET Core 2.1


*

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3.1 Add Student Model

You will get separate folders for Models, Views and Controllers in your project. Let's create a model class called Student as below


namespace ajaxPartial.Models
{
public class  Student
{
public string  Name { get; set; }
public int  CourseId { get; set; }
public string  Course { get; set; }
public string  Lab { get; set; }
public double  Marks { get; set; }
}
}

Let's create a method to return list of students


public static  List<Student> GetStudents () 
{ 

var students = new  List<Student>() { new Student { Name = "Hank Aaron", CourseId = 1, Course = "Computer Architecture", Lab = "Lab 01", Marks = 84}, new  Student{ Name = "Alfred Adler", CourseId = 2, Course = "Database Systems", Lab = "Lab 02", Marks = 70 }, new  Student { Name = "Conrad Aiken", CourseId = 1, Course = "Computer Architecture", Lab = "Lab 03", Marks = 73 }, new  Student { Name = "Buzz Aldrin", CourseId = 3, Course = "Data Structure and Algorithms", Lab = "Lab 04", Marks = 92 }, new  Student { Name = "Susan Anthony", CourseId = 4, Course = "Software Engineering", Lab = "Lab 01", Marks = 65 }, new  Student { Name = "Norman Ralph Augustine", CourseId = 2, Course = "Database Systems", Lab = "Lab 03", Marks = 59}, new  Student { Name = "Andy Bathgate", CourseId = 1, Course = "Computer Architecture", Lab = "Lab 02", Marks = 80 }, new  Student { Name = "Jimmy Carter", CourseId = 2, Course = "Database Systems", Lab = "Lab 01", Marks = 84 }, new  Student { Name = "Thomas Edison", CourseId = 4, Course = "Software Engineering", Lab = "Lab 04", Marks = 75 }, new  Student { Name = "Thomas Edison", CourseId = 3, Course = "Data Structure and Algorithms", Lab = "Lab 01", Marks = 60 }, new  Student { Name = "William Gladstone", CourseId = 2, Course = "Database Systems", Lab = "Lab 03", Marks = 69 }, new  Student { Name = "Mary Hirsch", CourseId = 2, Course = "Database Systems", Lab = "Lab 01", Marks = 78 }, new  Student { Name = "Derek Jeter", CourseId = 3, Course = "Data Structure and Algorithms", Lab = "Lab 02", Marks = 73 }, new  Student { Name = "Ted Kennedy", CourseId = 3, Course = "Data Structure and Algorithms", Lab = "Lab 03", Marks = 85 }, new  Student { Name = "Steve Lyons", CourseId = 2, Course = "Database Systems", Lab = "Lab 02", Marks = 79 }, new  Student { Name = "Benito Mussolini", CourseId = 4, Course = "Software Engineering", Lab = "Lab 04", Marks = 59 } };

return students; 
}

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3.2 Change Index method in HomeController

Go to HomeController and change Index method to get the list of students and pass it to the Index view.


public IActionResult Index() 
{ 
List students = Student.GetStudents(); 
return View(students); 
}

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3.3 Add Student list view

You can change the student Index view as below, add search form with student text box and courses drop down


<h1>Search Students</h1>
<br />
<form>
<div class="form-row">
<div class="form-group col-md-6">
<label for="Student">Student</label>
<input type="text" id="student" placeholder="Student" class="form-control">
</div>
<div class="form-group col-md-6">
<label for="Course">Course</label>
<select class="form-control">
<option value="1">Computer Architecture</option>
<option value="2">Database Systems</option>
<option value="3">Data Structure and Algorithms</option>
<option value="4">Software Engineering</option>
</select>
</div>
</div>
<div class="form-row">
<div class="form-group col-md-12">
<input id="btnSearch" type="button" class="btn btn-primary" value="Search"/>
</div>
</div>
</form>

Let's add a grid view below the search form, when initial page loads, it will show all the student records,


<table  class="table table-striped">
<thead>
<tr>
<th> Name </th>
<th> Course </th>
<th> Lab </th>
<th> Marks </th>
</tr>
</thead>
<tbody>
@foreach (var student in Model)
{
<tr>
<td> @student.Name </td>
<td> @student.Course </td>
<td> @student.Lab </td>
<td> @student.Marks </td>
</tr>
}
</tbody>
</table>

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3.4 Add js file to load students

Let's create javascript file to write js function for Index view and refer it from view as below,


<script  src="~/js/index.js"></script>

You can see the index.js file as below. Let's write the method to execute when search button click using jquery selector


$('#btnSearch').on('click', function  (e) { 
alert(); 
});

Let's run the application, you can see a search form and a list of students as below. When we click on the search button, we want to fetch students according to the search criteria.
You can find two ways to do that, load whole page when a button clicks or else refresh only the student list, the search form will not be rendered again. We can do that by passing an ajax request and loading a partial view.
In this developed application, search form and student list is available in the same page, let's split the two things into two views and load the second view on an ajax request

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3.5 Create a partial view for students

Let's create a partial view to hold the list of students and separate students grid from Index view, Go to Views folder and click on Add -> View,

In Add MVC View window, add a view name, select List as the view template, select Student as the model class, tick on Create as partial view and click on Add button

You can see _Students partial view as below, It's going to show a list of students in a grid layout

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3.6 Change data load methods

You can change the GetStudents method by passing a filter parameter, It will filter student list according to Student name and Course


public static  List GetStudents (StudentFilter filters) 
{ 

var students = new  List() { 
new Student { Name = "Hank Aaron", CourseId = 1, Course = "Computer Architecture", Lab = "Lab 01", Marks = 84}, 
new Student{ Name = "Alfred Adler", CourseId = 2, Course = "Database Systems", Lab = "Lab 02", Marks = 70 }, 
new Student { Name = "Conrad Aiken", CourseId = 1, Course = "Computer Architecture", Lab = "Lab 03", Marks = 73 }, 
new Student { Name = "Buzz Aldrin", CourseId = 3, Course = "Data Structure and Algorithms", Lab = "Lab 04", Marks = 92 
}, 
new Student { Name = "Susan Anthony", CourseId = 4, Course = "Software Engineering", Lab = "Lab 01", Marks = 65 }, 
new Student { Name = "Norman Ralph Augustine", CourseId = 2, Course = "Database Systems", Lab = "Lab 03", Marks = 59}, 
new Student { Name = "Andy Bathgate", CourseId = 1, Course = "Computer Architecture", Lab = "Lab 02", Marks = 80 }, 
new Student { Name = "Jimmy Carter", CourseId = 2, Course = "Database Systems", Lab = "Lab 01", Marks = 84 }, 
new Student { Name = "Thomas Edison", CourseId = 4, Course = "Software Engineering", Lab = "Lab 04", Marks = 75 }, 
new Student { Name = "Thomas Edison", CourseId = 3, Course = "Data Structure and Algorithms", Lab = "Lab 01", Marks = 60 }, 
new Student { Name = "William Gladstone", CourseId = 2, Course = "Database Systems", Lab = "Lab 03", Marks = 69 }, 
new Student { Name = "Mary Hirsch", CourseId = 2, Course = "Database Systems", Lab = "Lab 01", Marks = 78 }, 
new Student { Name = "Derek Jeter", CourseId = 3, Course = "Data Structure and Algorithms", Lab = "Lab 02", Marks = 73 }, 
new Student { Name = "Ted Kennedy", CourseId = 3, Course = "Data Structure and Algorithms", Lab = "Lab 03", Marks = 85 }, 
new Student { Name = "Steve Lyons", CourseId = 2, Course = "Database Systems", Lab = "Lab 02", Marks = 79 }, 
new Student { Name = "Benito Mussolini", CourseId = 4, Course = "Software Engineering", Lab = "Lab 04", Marks = 59 } }; 

if (!string.IsNullOrEmpty(filters.Student)) 
students = students.Where(s => s.Name.ToLower().Contains(filters.Student.ToLower())).ToList(); 

if (filters.CourseId != 0) 
students = students.Where(s => s.CourseId == filters.CourseId).ToList(); 

return students; 
}

Create StudentFilter model class as follows, we have to pass string value in textbox control and selected dropdown value


namespace ajaxPartial.Models 
{ 
public class  StudentFilter 
{ 
public string  Student { get; set; } 
public int  CourseId { get; set; } 
} 
}

Change Index action method implementation to call GetStudents method,
In the page load, it's going to call student load method with empty parameters (All option is selected in dropdown & empty text box)
When clicking on Search button, call student load method with parameters and pass it to the _Students partial view


namespace ajaxPartial.Controllers 
{ 
public class  HomeController : Controller 
{ 
public IActionResult Index() 
{ 
List students = Student.GetStudents(new StudentFilter()); 
return View(students); 
} 

[HttpPost] 
public IActionResult Students (StudentFilter filters)  
{ 
List students = Student.GetStudents(filters); 
return PartialView("_Students", students); 
} 
} 
}

You can see _Students partial view as below, It expects the list of Students and renders them in a table


@model IEnumerable<ajaxPartial.Models.Student>
<table class="table">
<thead>
<tr>
<th>
@Html.DisplayNameFor(model => model.Name)
</th>
<th>
@Html.DisplayNameFor(model => model.Course)
</th>
<th>
@Html.DisplayNameFor(model => model.Lab)
</th>
<th>
@Html.DisplayNameFor(model => model.Marks)
</th>
</tr>
</thead>
<tbody>
@foreach (var item in Model) {
<tr>
<td>
@Html.DisplayFor(modelItem => item.Name)
</td>
<td>
@Html.DisplayFor(modelItem => item.Course)
</td>
<td>
@Html.DisplayFor(modelItem => item.Lab)
</td>
<td>
@Html.DisplayFor(modelItem => item.Marks)
</td>
</tr>
}
</tbody>
</table>

When click on search button, it'll load list of students from _Students partial view into this div tag. Let's see how we can do that from JavaScript function


@using ajaxPartial.Models;
@model List<Student>

<h1>Search Students</h1>
<br />

<form>
<div class="form-row">
<div class="form-group col-md-6">
<label for="Student">Student</label>
<input type="text" id="student" placeholder="Student" class="form-control">
</div>
<div class="form-group col-md-6">
<label for="Course">Course</label>
<select class="form-control" id="course">
<option value="0">All</option>
<option value="1">Computer Architecture</option>
<option value="2">Database Systems</option>
<option value="3">Data Structure and Algorithms</option>
<option value="4">Software Engineering</option>
</select>
</div>
</div>
<div class="form-row">
<div class="form-group col-md-12">
<input id="btnSearch" type="button" class="btn btn-primary" value="Search" />
</div>
</div>
</form>

<div id="students"> </div>

<script src="~/js/index.js"></script>

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3.7 Load partial view from javascript method

Go to index.js file, load student list when page loads, we can call it from document.ready event

When clicking on the search button, we can issue an ajax request with student text box and course drop-down values.

When it succeeds, load _Students partial view into students div tag. We can identify error and stack trace information if anything bad happens
In Ajax request, pass the Controller - Action URL, type of the request as POST, filter data as a JSON object and the response in form of an HTML string since action method returns a partial view
We can specify the async parameter for the Ajax request, by default it's async - true, If we want to make a synchronous request we can set async to false, sometimes browser can be blocked in an async request, so we have to modify it accordingly
In Ajax request, we can set cache options as well. We can set cache - true for GET & HEAD requests only, If we want to cache the result of a method, we can set a cache attribute to true


$(function  () { 
GetStudents(); 
}); 

$('#btnSearch').on('click', function  (e) { 

var filters = { 
student: $('#student').val(), 
courseId: $('#course').val() 
}; 

GetStudents(filters); 
}); 

function GetStudents(filters) { 

$.ajax({ 
url: '/Home/Students', 
type: 'POST',  
cache: false, 
async: true, 
dataType: "html",  
data : filters 
})
.done(function (result) { 
$('#students').html(result); 
}).fail(function (xhr) { 
console.log('error : ' + xhr.status + ' - ' + xhr.statusText + ' - ' + xhr.responseText); 
});


}

We can comment out GetStudents method in Index action method, students are loaded from document.ready event in the js file

Let's run the application and see what happens, it shows search form and student list partial view when the page loads

Let's try to filter students from a course and student name when click on Search button it's going to load the partial view with filtered data

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4 Download

You can download the source code from TechNet Gallery, ASP.NET Core : loading a partial view

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4.2 GitHub

You can clone the source code from GitHub, ajax-partialview

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5 Conclusion

In this article, we used ASP.NET Core MVC to develop an application and load a partial view when a button clicks. In the main view, the search form is not getting rendered again when search button clicks, it only renders the partial view from an AJAX request.

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6 References

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