title: cant add new custom Model Binder ? error An item with the same key has already been added
body: <p>I m trying to add a new custom Model Binder but not successful. Below is my code and in term of basic working (removing formatting and converting 2,345.34 to 234534) it is doing fine: </p>
  
  <pre><code> public class TransactionModelBinder : IModelBinder
      {
          public object BindModel(ControllerContext controllerContext,
              ModelBindingContext bindingContext)
          {
              ValueProviderResult valueResult = bindingContext.ValueProvider.GetValue("Transaction.Price");
              ModelState modelState = new ModelState { Value = valueResult };
              object actualValue = null;
              object newValue = null;
              try
              {
                  if (!string.IsNullOrEmpty(valueResult.AttemptedValue))
                  {
                      newValue = valueResult.AttemptedValue.Replace(",", "");
                  }
                  actualValue = Convert.ToDecimal(newValue,
                      CultureInfo.CurrentCulture);
              }
              catch (FormatException e)
              {
                  modelState.Errors.Add(e);
              }
  
              bindingContext.ModelState.Add(bindingContext.ModelName, modelState);
              return actualValue;
          }
      }
  </code></pre>
  
  <p>My Global.asax code is given below:</p>
  
  <pre><code> protected void Application_Start()
      {
          ModelBinders.Binders.Add(typeof(decimal), new CurrencyModelBinder());
          ModelBinders.Binders.Add(typeof(decimal), new TxTransactionModelBinder());
  
          AreaRegistration.RegisterAllAreas();
  
          WebApiConfig.Register(GlobalConfiguration.Configuration);
          FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
          RouteConfig.RegisterRoutes(RouteTable.Routes);
          BundleConfig.RegisterBundles(BundleTable.Bundles);
         // RouteTable.Routes.MapHubs();
  
  
      }
  </code></pre>
  
  <p>Issue:
  On running code TransactionModelBinder work fine but in global.asax I got the follwoing error:</p>
  
  <p><strong>An item with the same key has already been added.</strong></p>
  
  <p>I can understand <code>typeof(decimal)</code> in two custom binders is causing this issue.</p>
  
  <p>Can you please guide and help me on how to fix this.</p>