FieldRenderingControl of SPField throws an exception for Survey List

Question

I have created a Survey List in MOSS 2007. The field used in the survey is of 'Choice' type. While getting the field value in a custom web part program on another page, the FieldRenderingControl of SPField is throwing an exception.

The code for webpart is :

    SPSite mySite = SPContext.Current.Web.Site;

            SPWeb myWeb = mySite.OpenWeb();

            SPList mylist = myWeb.Lists[surveyname];

            int surveyUserCount = mylist.ItemCount;
        try
         {

            if (surveyUserCount > 0)
            {
                foreach (SPListItem item in mylist.Items)
                {

                    foreach (SPField field in item.Fields)
                    {
                        if (field.TypeAsString == "Choice")
                        {

                            string check = Convert.ToString(field.FieldRenderingControl.ItemFieldValue);
                            if (check != "")
                        }
                   }
                }
             }
           }

The exception thrown is : 'field.FieldRenderingControl.ItemFieldValue' threw an exception of type 'System.InvalidOperationException'
base {System.SystemException} = {"Operation is not valid due to the current state of the object."}

Answer 1

You need to increase connection keys in your web config file as there is a good chance the survey may have a lot of items.

Add the following entries in the app settings section inside the web.config file for your web application where the site collection is located.

<appSettings> <add key="aspnet:MaxHttpCollectionKeys" value="8000" /> </appSettings>

Let us know if the above the solves your issue or not.

Answer 2

The problem was that FieldRenderingControl is created only on Edit/DispForm page. Otherwise it will always give an exception.

However, by making use of SPFieldChoice and StringCollection, i was able to get both the count and index of the selected option. Here is the snippet:

                 try
             {

                 if (surveyUserCount > 0)
                 {
                     foreach (SPListItem item in myList.Items)
                     {
                         responseUserTotal = 0;



                         foreach (SPField field in item.Fields)
                         {
                             int tempIndex = 0;

                             if (field.TypeAsString == "Choice")
                             {
                                 SPFieldChoice dropDown = field as SPFieldChoice;
                                 StringCollection eachQuesChoices = dropDown.Choices;
                                 tempIndex = eachQuesChoices.IndexOf(Convert.ToString(item[field.Title]));
                                 if (tempIndex >= 0)
                                 {
                                     responseUserTotal += getRating(eachQuesChoices.Count, tempIndex);
                                 }


                             }
                         }

                         responseSurveyTotal += responseUserTotal;

                     }

                     responseSurveyTotal = responseSurveyTotal / surveyUserCount;
                 }
             }