ASP.NET MVC无法从本地SQL Server Express数据库检索数据

Question

First of all please excuse me, but I am a total newbie when it comes to ASP.NET as I'm trying to learn some of it at the moment.

I am following one of online tutorials for ASP.NET MVC4, but am using Visual Studio 2015 Community (MVC5) and SQL Server 2014 Express.

The goal is to retrieve data from a local SQL Server Express database using Windows authentication. In this case, employees with their id, name, city and gender. At this moment I get the following error:

An exception of type 'System.Data.Entity.Core.EntityException' occurred in EntityFramework.SqlServer.dll but was not handled in user code

Additional information: The underlying provider failed on Open.

The database looks like this - Ids as int , rest as varchar(50) :

Employee.cs located in Model:

[Table("tblEmployee")]
public class Employee
{
        public int EmployeeId { get; set; }
        public string Name { get; set; }
        public string Gender { get; set; }
        public string City { get; set; }
}

EmployeeContext.cs :

public class EmployeeContext : DbContext
{
    public DbSet<Employee> Employees { get; set; }
}

EmployeeController.cs :

public class EmployeeController : Controller
{
        // GET: Employee
        public ActionResult Details(int id)
        {
            EmployeeContext employeeContext = new EmployeeContext();
            Employee employee = employeeContext.Employees.Single(emp => emp.EmployeeId == id);
            return View(employee);
        }
}

The view - Details.cshtml :

@model MVCDemo.Models.Employee

@{
    ViewBag.Title = "Employee Details";
}

<h2>Employee Details</h2>
<table style="font-family:Arial">
    <tr>
        <td>
            <b>Employee ID:</b>
        </td>
        <td>
            @Model.EmployeeId
        </td>
    </tr>
    <tr>
        <td>
            <b>Name:</b>
        </td>
        <td>
            @Model.Name
        </td>
    </tr>
    <tr>
        <td>
            <b>Gender:</b>
        </td>
        <td>
            @Model.Gender
        </td>
    </tr>
    <tr>
        <td>
            <b>City:</b>
        </td>
        <td>
            @Model.City
        </td>
    </tr>
</table>

And finally, the connection string from web.config in the root (I made sure) directory:

<add name="EmployeeContext" 
     connectionString="Data Source=DESKTOP-6RQ94N9\MAIN;Initial Catalog=Sample;Integrated Security=SSPI"
     providerName="System.Data.SqlClient" />

The default connectionString="Data Source=.\\SQLEXPRESS; simply didn't work. Anyways, Server explorer shows a successful data connection to the database, I can browse the tables and their columns within the Visual Studio.

When I launch the project and try for example:

http://localhost/MVCDemo/Employee/Details/1

The site just keeps loading for a while and then the above mentioned exception occurs at

Employee employee = employeeContext.Employees.Single(emp => emp.EmployeeId == id);

When I debug the application, employeeContext.Employees.Local.Count shows 0, so I guess there is no data being retrieved.

Thank you very much for help!

Answer 1

Well, see How to: Access SQL Server Using Windows Integrated Security for details if using that option.

You're able to connect to SQL as "you" within Visual Studio (or SSMS) because you're running Visual Studio as "you" ( your Windows user account). Your Asp.Net site isn't .

You could use SQL Authentication (instead) so your application (ASP.Net) and data store (SQL) users are separate and therefore can be managed separately, not have to deal with (creation of) actual Windows users. This will be more apparent if/when you go to production/hosting (eg web server and sql server are separate, no Windows "domain", etc.).

As for connectivity issues see How to Troubleshoot Connecting to the SQL Server Database Engine

Hth.

Answer 2

Are you sure that employeeContext.Employees.Local.Count even tries to call a database? What you need is to check the name of your SQL Server Express instance. Go to your folder with Microsoft SQL Server (your version) in all programs in the Start Menu and click Sql Server Configuration Manager . In SQL Server Services tab you will see SQL Server (NAME) , usually it shows SQL Server (SQLEXPRESS) if you did not change the name during the installation.
Moreover, if you are able to access SQL Server from your Visual Studio with SQLEXPRESS name then you can easily access it from the ASP.NET website that you run locally. One of my projects has the following connection string:

<add name="DatabaseContext" connectionString="Data Source=DESKTOP-111111N\SQLEXPRESS;Initial Catalog=Sample;Integrated Security=True;Connect Timeout=15;Encrypt=False;TrustServerCertificate=False" providerName="System.Data.SqlClient" />

And please try to make a call to your database like this: employeeContext.Employees.Count() .
I hope that will help you!

UPDATE

Please also check what connection string is set in your Database Context class constructor, for my project it is base("DatabaseContext") :

public class DatabaseContext : DbContext
{
    public DatabaseContext()
        : base("DatabaseContext")
    {
    }

}

And for your project it will be base("EmployeeContext") .

Answer 3

Well, in this case I've actually made a workaround by creating an user with SELECT permission and updated my connection string with login credentials.

After that, I've successfully retrieved the information I needed from the database. Thank you all for your help!