ASP.NET MVC Database access

Question

I've been trying to use a preexisting database in my ASP.NET MVC project. I create a "Data Connection" to my (Microsoft SQL)Database (".\SQLEXPRESS.Databases"), which has the table "Test". This table has two columns, "ID (int)" and "name (nvarchar(MAX))".

In the "Models" folder I put this new class:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

using System.Data.Entity;

namespace MvcMovie.Models
{
    public class Test
    {
        public int ID { get; set; }
        public string name { get; set; }
    }
}

Then (in "Controllers") I have a new Controller, "HelloWorldController". In this I have this function:

    public ActionResult Index()
    {
        DataSet data;
        DataTable table;

        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            connection.Open();

            SqlCommand select = new SqlCommand("SELECT * FROM Test", connection);

            SqlDataAdapter adapter = new SqlDataAdapter();
            adapter.SelectCommand = select;

            data = new DataSet();
            adapter.Fill(data, "Test");

            table = data.Tables[0]; //is the [0] really correct?
        }

        return View(/* HOW DO I GET THE TABLE TO THE VIEW? */);
    }

Now I would like to display the rows of the table in my "Index.cshtml" file (in "Views"). How do I get the table from the Controller to the view? What I found was with "@model" and "IEnumerable", but that does not work, since I cannot convert my table.

@model IEnumerable<MyProject.Models.Test>

@{
    ViewBag.Title = "Index";
}

<h2>Index</h2>

@foreach (var item in Model) {
    <p>blaaaah</p>
}

Now there are three questions:
1. Am I doing something completely wrong? (Method of DB-Access,..)
2. Is there an easier way to do this? (Without all adapter,.. stuff)
3. If !1&&!2, How do I get it to work? (Get the view file to "know" my table)

Thanks for help,
Regards,
Caba

Darin Dimitrov · Accepted Answer · 2012-05-02 14:41:41Z

13

I'd recommend you using view models and get rid of DataSets and Tables. Let's forget about those data types. They are legacy.

For example you could have a method (which you would eventually externalize into a repositorhy to avoid polluting your controller code with database access):

public IEnumerable<Test> GetTests()
{
    using (var conn = new SqlConnection(connectionString))
    using (var cmd = conn.CreateCommand())
    {
        conn.Open();
        cmd.CommandText = "SELECT ID, name FROM Test";
        using (var reader = cmd.ExecuteReader())
        {
            while (reader.Read())
            {
                yield return new Test
                {
                    ID = reader.GetInt32(reader.GetOrdinal("ID")),
                    name = reader.GetString(reader.GetOrdinal("name")),
                }
            };
        }
    }

}

and then your controller action:

public ActionResult Index()
{
    IList<Test> tests = GetTests().ToList();
    return View(tests);
}

So far so good. Finally the corresponding strongly typed view to display the results:

@model IList<Test>
<table>
    <thead>
        <tr>
            <th>ID</th>
            <th>Name</th>
        </tr>
    </thead>
    <tbody>
        @for (var i = 0; i < Model.Count; i++)
        {
            <tr>
                <td>@Html.DisplayFor(x => x[i].ID)</td>
                <td>@Html.DisplayFor(x => x[i].name)</td>
            </tr>
        }
    </tbody>
</table>

or use the WebGrid helper if you prefer:

@model IList<Test>
@{
    var grid = new WebGrid(Model);
}
@grid.GetHtml()

answered May 2, 2012 at 14:41

Darin Dimitrov

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3 Comments

Cabadath Over a year ago

Thank you for the detailed instructions. I really like your solution. Up to now, I have never seen that "yield" ._. but that's not really an issue. I've rewritten my stuff (the changes were not that big) to match your structure and I'm pretty happy with the result. Thanks a lot.

KSK Over a year ago

Just a thought... I doubt if the yield return is a good thing to do. Isn't it better to return an IList<Test> instead of IEnumerable<Test>? Is there an advantage in using the yield return?

Darin Dimitrov Over a year ago

@KSK, using an iterator allows you to lazily load the data set. For example if you need to display only the first 50 rows in your view it would be a complete waste to load all the results in memory and throw them out. Obviously in my example I am iterating on all the results in the view, but in a real world application you are probably wanting to do some pagination.

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