Web API in ASP.NET with OData - Problem in the view

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Web API in ASP.NET with OData - Problem in the view

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#1 by (0 votes)

1

I have a Web API in ASP.NET with OData and I can consume without problems of the service, but I can not get the view to print A table. I'm starting with .NET and with MVC .

Model:

namespace exchange_rates
{
    using System;
    using System.Collections.Generic;

    public partial class CurrentValue
    {
        public int Id { get; set; }
        public System.DateTime Date { get; set; }
        public string Currency { get; set; }
        public double Rate { get; set; }
    }
}

Controller:

namespace exchange_rates.Controllers
{
    public class CurrentValuesController : ODataController    
    {
        private db_test_bce_Entities db = new db_test_bce_Entities();

        // GET: odata/CurrentValues
        [EnableQuery]
        public IQueryable<CurrentValue> GetCurrentValues()
        {
            return db.CurrentValues;
        }

        // GET: odata/CurrentValues(5)
        [EnableQuery]
        public SingleResult<CurrentValue> GetCurrentValue([FromODataUri] int key)
        {
            return SingleResult.Create(
                db.CurrentValues.Where(currentValue => currentValue.Id == key)
            );
        }
    }
}

File code WebApiConfig.cs :

namespace exchange_rates
{
    public static class WebApiConfig
    {
        public static void Register(HttpConfiguration config)
        {
            ODataConventionModelBuilder builder = new ODataConventionModelBuilder();
            builder.EntitySet<CurrentValue>("CurrentValues");
            config.Routes.MapODataServiceRoute("odata", "odata", builder.GetEdmModel());
        }
    }
}

View:

@model IEnumerable<exchange_rates.CurrentValue>

@{
    Layout = null;
}

<!DOCTYPE html>

<html>
    <head>
        <meta name="viewport" content="width=device-width" />
        <title>CurrenciesTable</title>
    </head>
    <body>
        <table class="table">
            <tr>
                <th>
                    @Html.DisplayNameFor(model => model.Date)
                </th>
                <th>
                    @Html.DisplayNameFor(model => model.Currency)
                </th>
                <th>
                    @Html.DisplayNameFor(model => model.Rate)
                </th>
                <th></th>
            </tr>

            @foreach (var item in Model)
            {
                <tr>
                    <td>
                        @Html.DisplayFor(modelItem => item.Date)
                    </td>
                    <td>
                        @Html.DisplayFor(modelItem => item.Currency)
                    </td>
                    <td>
                        @Html.DisplayFor(modelItem => item.Rate)
                    </td>
                </tr>
            }
        </table>
    </body>
</html>

Online error that says @foreach (var item in Model) :

System.NullReferenceException: Object reference not set as an instance of an object.

asp.net-mvc asp.net-web-api odata

asked by yuya 20.03.2017 в 12:34

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1 answer

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score 0 · Answer 1

You could avoid the error by adding this line of code in your view.

@model IEnumerable<exchange_rates.CurrentValue>

@{
    Layout = null;
}

<!DOCTYPE html>

<html>
<head>
    <meta name="viewport" content="width=device-width" />
    <title>CurrenciesTable</title>
</head>
<body>
    <table class="table">
        <tr>
            <th>
                @Html.DisplayNameFor(model => model.Date)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Currency)
            </th>
            <th>
                @Html.DisplayNameFor(model => model.Rate)
            </th>
            <th></th>
        </tr>

        @foreach (var item in Model)
        {
            <tr>
                <td>
                    @Html.DisplayFor(modelItem => item.Date)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.Currency)
                </td>
                <td>
                    @Html.DisplayFor(modelItem => item.Rate)
                </td>
            </tr>
        }
    </table>
</body>
</html>

Now, your controller is missing a detail that I'm not catching.

EDIT : I think the driver problem might look like this:

namespace exchange_rates.Controllers
{
    public class CurrentValuesController : Controller
    {
        public async Task<ActionResult> Index()
        {
            var client = new HttpClient();
            var response = await client.GetAsync("LA_URL_DE_TU_API");
            var valores = await response.Content.ReadAsAsync<IEnumerable<CurrentValue>>();
            
            return View(valores);
        }
    }
}