Web Service C＃ASP.NET无法发出请求

Question

I'm in a proyect where I have to fill a textbox (as if it was a select control) with data requested from a Web Service while the user is writing in the textbox.

The web service is developed in the same solution.

The problem is when I make a request from the client-side it throws me:

"Failed to load http://.../wsConsultaAfiliados.asmx: No 'Access-Control-Allow-Origin' header is present on the requested resource.

I've searching for a while and I read that is a problem of CORS. However, I don't understand why. I'm requesting the data to the web service from the client-side which are in the same domain.

For what I searched I understand that CORS is for security reasons when you ask data from X domain to Y domain.

It's the first time I consume web service and I'm a bit lost about the scheme I should follow.

Add code

public class wsConsultaAfiliados : System.Web.Services.WebService
    {

        /// <summary>
        /// Busca una lista de Afiliados que coincidan con los parámetros de entrada. Devuele DataTable.
        /// </summary>
        /// <returns></returns>     
        [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
        [WebMethod]
        public DataTable ConsultarAfiliados(string oPrefixText)
        {
            var listaAfiliados = GetAfiliados(oPrefixText);

            return listaAfiliados;
        }

        /// <summary>
        /// Devuelve un DataTable con Codigo y Nombre del afiliado.
        /// </summary>
        /// <param name="oPrefixText"></param>
        /// <returns></returns>
        public DataTable GetAfiliados(string oPrefixText)
        {
            negPrevision neg = new negPrevision();
            return neg.obtenerAfiliadosPorNombre(oPrefixText);
        }
    }

Here's the code from the web services. It ask for data to the logic layer.

Answer 1

Update your web.config like this to allow every request

<system.webServer>
    <httpProtocol>
      <customHeaders>
        <add name="Access-Control-Allow-Origin" value="*" />
      </customHeaders>
    </httpProtocol>
</system.webServer>

For IIS 7.5+ and Rewrite 2.0 you can use

<system.webServer>
   <httpProtocol>
     <customHeaders>
         <add name="Access-Control-Allow-Headers" value="Origin, X-Requested-With, Content-Type, Accept" />
         <add name="Access-Control-Allow-Methods" value="POST,GET,OPTIONS,PUT,DELETE" />
     </customHeaders>
   </httpProtocol>
        <rewrite>            
            <outboundRules>
                <clear />                
                <rule name="AddCrossDomainHeader">
                    <match serverVariable="RESPONSE_Access_Control_Allow_Origin" pattern=".*" />
                    <conditions logicalGrouping="MatchAll" trackAllCaptures="true">
                        <add input="{HTTP_ORIGIN}" pattern="(http(s)?://((.+\.)?domain1\.com|(.+\.)?domain2\.com|(.+\.)?domain3\.com))" />
                    </conditions>
                    <action type="Rewrite" value="{C:0}" />
                </rule>           
            </outboundRules>
        </rewrite>
 </system.webServer>