asp.net mvc custom model binder

Question

My custom model binder which has been working perfectly has starting giving me errors

details below

An item with the same key has already been added. Description: 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.

Exception Details: System.ArgumentException: An item with the same key has already been added.

Source Error:

Line 31: { Line 32: string key = bindingContext.ModelName; Line 33: var doc = base.BindModel(controllerContext, bindingContext) as Document; Line 34: Line 35: // DoBasicValidation(bindingContext, doc);

Source File: C:\Users\Bich Vu\Documents\Visual Studio 2008\Projects\PitchPortal\PitchPortal.Web\Binders\DocumentModelBinder.cs Line: 33

Stack Trace:

[ArgumentException: An item with the same key has already been added.] System.ThrowHelper.ThrowArgumentException(ExceptionResource resource) +51 System.Collections.Generic.Dictionary2.Insert(TKey key, TValue value, Boolean add) +7462172 System.Linq.Enumerable.ToDictionary(IEnumerable1 source, Func2 keySelector, Func2 elementSelector, IEqualityComparer1 comparer) +270 System.Linq.Enumerable.ToDictionary(IEnumerable1 source, Func2 keySelector, IEqualityComparer1 comparer) +102 System.Web.Mvc.ModelBindingContext.get_PropertyMetadata() +157 System.Web.Mvc.DefaultModelBinder.BindProperty(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor) +158 System.Web.Mvc.DefaultModelBinder.BindProperties(ControllerContext controllerContext, ModelBindingContext bindingContext) +90 System.Web.Mvc.DefaultModelBinder.BindComplexElementalModel(ControllerContext controllerContext, ModelBindingContext bindingContext, Object model) +50 System.Web.Mvc.DefaultModelBinder.BindComplexModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +1048 System.Web.Mvc.DefaultModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) +280 PitchPortal.Web.Binders.documentModelBinder.BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) in C:\Users\Bich Vu\Documents\Visual Studio 2008\Projects\PitchPortal\PitchPortal.Web\Binders\DocumentModelBinder.cs:33 System.Web.Mvc.ControllerActionInvoker.GetParameterValue(ControllerContext controllerContext, ParameterDescriptor parameterDescriptor) +257 System.Web.Mvc.ControllerActionInvoker.GetParameterValues(ControllerContext controllerContext, ActionDescriptor actionDescriptor) +109 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +314 System.Web.Mvc.Controller.ExecuteCore() +105 System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +39 System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +7 System.Web.Mvc.<>c_DisplayClass8.b_4() +34 System.Web.Mvc.Async.<>c_DisplayClass1.b_0() +21 System.Web.Mvc.Async.<>c__DisplayClass81.b__7(IAsyncResult _) +12 System.Web.Mvc.Async.WrappedAsyncResult1.End() +59 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +44 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +7 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +8677678 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

any ideas guys? Thanks

Post some code of what you are doing in your binder. Most likely the error is just what's in the stack trace - you are trying to add an item into a collection but that item (or an item with the same key) is already present in it. This error often happens when you are copying collection, maybe when you iterate a collection in a for loop but are also trying to modify items in that same collection, etc.. — mare
public override object BindModel(ControllerContext controllerContext, ModelBindingContext bindingContext) { HttpRequestBase request = controllerContext.HttpContext.Request; string subject = request.Form.Get("doc.title"); string key = bindingContext.ModelName; var doc = base.BindModel(controllerContext, bindingContext) as Document; — mike
The faliure happens very early in the model binding code, from what I know asp.net model bindin works by getting values from querystring, post values etc and then adds then to some sort of dictionary, I am not trying to add anything to the collection, the built in model binding does that. The question is why would it be trying to add the same key — mike
ignore the first 2 HttpRequestBase request = controllerContext.HttpContext.Request; string subject = request.Form.Get("doc.title"); — mike

queen3 queen3 · Accepted Answer · 2010-05-10T12:59:32

See here, you probably got the same issue.

And please don't ask same question several times. You can just edit it.

asp.net mvc custom model binder

1 Answers