Asp.net WEB API for frondend and backend

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C#

ASP.NET

MVC5

i have a project i'm doing in C# ASP.Net MVC5 as my backend,and my frontend is also in C#.how will i bind the two for them to communicate.i'm using a search engine in my frontend to get data from the backend and SQL server.i need your good answers.
I have 3 tables,Students,Courses and Student_courses.my backend works well,i am confused on how to use the frontend to run queries to get results.i can't use the same method i used on the backend for the frontend.i don't need api again.query to get results i need

What I have tried:

this is my search view for the front end

@model UniScore.ViewModels.StudentCoursesViewModel

@{

    Layout = "~/Views/Shared/_Layout2.cshtml";
}
<h1 align="center">SEARCH STUDENT</h1>
<br />

<div class="container">
    @using (Html.BeginForm("Search", "Search", FormMethod.Get))
    {
        @Html.AntiForgeryToken()

        <div class="form-horizontal">

            <p>Please type in your Student ID and First Name</p>
            <hr />
            @Html.ValidationSummary(true, "", new { @class = "text-danger" })
            <div class="form-group">
                @Html.LabelFor(model => model.FirstName, htmlAttributes: new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.EditorFor(model => model.FirstName, new { htmlAttributes = new { @class = "form-control" } })
                    @Html.ValidationMessageFor(model => model.FirstName, "", new { @class = "text-danger" })
                </div>
            </div>
            <br />
            <div class="form-group">
                @Html.LabelFor(model => model.id_Student, htmlAttributes: new { @class = "control-label col-md-2" })
                <div class="col-md-10">
                    @Html.EditorFor(model => model.id_Student, new { htmlAttributes = new { @class = "form-control" } })
                    @Html.ValidationMessageFor(model => model.id_Student, "", new { @class = "text-danger" })
                </div>
            </div>
            <br />

            <div class="form-group">
                <div class="col-md-offset-2 col-md-10">
                    <input type="submit" value="SearchResults" class="btn btn-default" />
                </div>
            </div>
        </div>

    }
</div>

Student table has(id_student,firstname and lastname),
Course table has(id_course,code,course name)
Student_course table(id,student_id,course_id,mark,grade)...now every student can do a lot of courses.i didn't use foreign keys.
How can i use the view to display the courses a student is undertaking in the search,which linq query will i use to display values in the controller.if you can give me idea of how to code in the controller i will be fine.