我在我的mvc项目中使用webapi，当我从浏览器向api调用发出请求时，我收到以下错误：
我正在使用.netFramework 4.0
异常详细信息：
应用程序中的服务器错误。值'application / json的格式; charset = utf-8'无效。
说明
An unhandled exception occurred during the execution of the current web
request. Please review the stack trace for more information about the
error and where it originated in the code.
异常详细信息：
System.FormatException: The format of value 'application/json;
charset=utf-8' is invalid.
来源错误：
An unhandled exception was generated during the execution of the current
web request. Information regarding the origin and location of the
exception can be identified using the exception stack trace below.
堆栈追踪：
[FormatException: The format of value 'application/json; charset=utf-8'
is invalid.]
System.Net.Http.Headers.MediaTypeHeaderValue.CheckMediaTypeFormat(String
mediaType, String parameterName) +119919
System.Net.Http.Headers.MediaTypeHeaderValue..ctor(String mediaType) +23
System.Net.Http.ObjectContent.BuildHeaderValue(String mediaType) +63
System.Net.Http.ObjectContent`1..ctor(T value, MediaTypeFormatter
formatter, String mediaType) +66
System.Net.Http.HttpRequestMessageExtensions.CreateResponse(HttpRequestMessage request, HttpStatusCode statusCode, T value, HttpConfiguration configuration) +892
System.Net.Http.HttpRequestMessageExtensions.CreateResponse(HttpRequestMessage request, HttpStatusCode statusCode, T value) +104
System.Web.Http.Dispatcher.HttpControllerDispatcher.HandleException(HttpRequestMessage request, Exception exception, HttpConfiguration configuration) +191
System.Web.Http.Dispatcher.HttpControllerDispatcher.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) +284
System.Net.Http.DelegatingHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) +41
System.Web.Http.HttpServer.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) +347
System.Net.Http.HttpMessageInvoker.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken) +55
System.Web.Http.WebHost.HttpControllerHandler.BeginProcessRequest(HttpContextBase httpContextBase, AsyncCallback callback, Object state) +316
System.Web.Http.WebHost.HttpControllerHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +77
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +103
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155
我在谷歌搜索但找不到合适的解决方案。