CS0234：类型或名称空间名称“ Description”在名称空间“ System.Web.Http”中不存在（您是否缺少程序集引用？）

Question

I'm having namespaces error in ASP.Net MVC WebAPI. I'm using MVC 4 with .Net Framework 4.5, while running the application It works but on the click of API it displays error like below.

    ------------------------------------------------------------------------------------
    Server Error in '/' Application.

    Compilation Error

    Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately.

    Compiler Error Message: CS0234: The type or namespace name 'Description' does not exist in the namespace 'System.Web.Http' (are you missing an assembly reference?)

    Source Error:
    Line 1:  @using System.Web.Http
    Line 2:  @using System.Web.Http.Description
    Line 3:  @using System.Collections.ObjectModel
    Line 4:  @using SmartCare360APIs.Areas.HelpPage.Models

    Source File: e:\Projects\SmartCare 360\Code\SmartCare360APIs\SmartCare360APIs\Areas\HelpPage\Views\Help\Index.cshtml    Line: 2

    Show Detailed Compiler Output:
    Show Complete Compilation Source:

    Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.6.1637.0
    -----------------------------------------------------------------------------------

Below is the where namespace is missing. I tried to reinstall mvc 4 but it comes with many more error.

Page : **ApiGroup.cshtml**

 @using System.Web.Http
 @using System.Web.Http.Description
 @using SmartCare360APIs.Areas.HelpPage
 @using SmartCare360APIs.Areas.HelpPage.Models
 @model IGrouping<string, ApiDescription>

 <h2 id="@Model.Key">@Model.Key</h2>
 <table class="help-page-table">
 <thead>
                <tr><th>API</th><th>Description</th></tr>
            </thead>
            <tbody>
            @foreach (var api in Model)
            {
                <tr>
                    <td class="api-name"><a href="@Url.Action("Api", "Help", new { apiId = api.GetFriendlyId() })">@api.HttpMethod.Method @api.RelativePath</a></td>
                    <td class="api-documentation">
                    @if (api.Documentation != null)
                    {
                        <p>@api.Documentation</p>
                    }
                    else
                    {
                        <p>No documentation available.</p>
                    }
                    </td>
                </tr>
            }
            </tbody>
        </table>

Answer 1

Try below things:

1) Try Setting 'Copy local: true' in Properties tab in References\\System.Web.Http

2) If above doesn't work , try Uninstalling Package Microsoft.AspNet.WebApi in the NuGet Package Console and then re-install it.

Answer 2

Sometimes de reference to System.Web doesn't recognize the correct version.

Try to add it manually using Browse option on Add Reference.

Answer 3

It was .Net framework issue. I've Updated .Net framework to latest and error has gone. Still I'm not sure that this is the resolution but somehow It worked form me.

Thanks for the response!