The 'SelectedIndex' and 'SelectedValue' attributes are mutually exclusive.

Hi,

I have a Custom DropDownList that is causing the following error:
 

                    The 'SelectedIndex' and 'SelectedValue' attributes are mutually exclusive.


For some reason, this DropDownList works with some data and not others - I guess this would suggest the data is the problem (i have attached data results as well)
The DropDownList retrieves a datalist (name,value fields) from the database and binds them to the inherited control.
The inherited control is also a DropDownList extension that enables us to add empty fields to top or bottom of list.

Any help here would be appreciated. This has realy stumped me.

I have provided all code below:


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using System;
using System.Data;
using Microsoft.Practices.EnterpriseLibrary.Common;
using Microsoft.Practices.EnterpriseLibrary.Data;
using Microsoft.Practices.EnterpriseLibrary.ExceptionHandling;
using Microsoft.Practices.EnterpriseLibrary.Logging;
using MWeb.Data;
using DKC.Data;

namespace DKC.Web.UI.CustomControls
{      
      ///<summary>
      /// Service Custom Dropdown List
      ///</summary>
      public class ServiceDropDownList :  MWeb.Web.UI.CustomControls.ExtraItemDropDownList
      {                                                      
            public override string DataTextField
            {
                  get
                  {                
                        return (base.DataTextField == string.Empty) ? "DataTextField" : base.DataTextField;
                  }
                  set
                  {                  
                        base.DataTextField = value;
                  }
            }

            public override string DataValueField
            {
                  get
                  {
                        return (base.DataValueField == string.Empty) ? "DataValueField" : base.DataValueField;
                  }
                  set
                  {
                        base.DataValueField = value;
                  }
            }

            protected override void Fill()
            {
                  try
                  {
                        this.DataSource = DataProviderFactory.GetServiceDataProvider().DataReaderProvider.GetList();

                        /************** THE DATA RETURNED FROM THE ABOVE CALL *********

                        2      Asset Management
                        1      Funds Management
                        3      Investment Opportunities

                        ****************/
                        this.DataBind(); /************ ERROR BUBBLES THROUGH HERE (see ExtraItemDropDownList as this overrides the DropDownList DataBind method)! ***********************/
                  }
                  catch ( Exception ex )
                  {
                        bool rethrow = ExceptionPolicy.HandleException( ex, "Data Policy" );
                        if(rethrow)
                        {
                              throw;
                        }
                  }
            }
      }
}


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using System;
using System.Web.UI.WebControls;
using System.Collections;
using System.ComponentModel;

namespace MWeb.Web.UI.CustomControls
{      
      /// <summary>
      /// Extra Item Position in DDL
      /// </summary>
      public enum ExtraItemPosition
      {
            Top,
            Bottom
      };

      /// <summary>
      /// Base Class for Extra Item <code>DropDownList</code>s
      /// </summary>
      public abstract class ExtraItemDropDownList : System.Web.UI.WebControls.DropDownList
      {      
            #region Constants

            public const string DEFAULT_EXTRAITEM_TEXT = "None";
            public const string DEFAULT_EXTRAITEM_VALUE = "0";

            public const string DEFAULT_DATATEXT_FIELD = "DataTextField";
            public const string DEFAULT_DATAVALUE_FIELD = "DataValueField";

            #endregion

            #region Constructor

            public ExtraItemDropDownList()
            {
            }

            #endregion

            #region Abstract and Virtuals

            protected abstract void Fill();
            protected virtual void Refresh()
            {
                  this.Fill();
            }

            #endregion

            #region Overrides

            ///<summary>
            ///Fills the DropDownList with items from the database on the first request
            ///If PopulateOnLoad is true. Will populate itself on any request where
            ///IsDirtyData is true.
            ///</summary>
            protected override void OnLoad(EventArgs e)
        {            
            base.OnLoad(e);
            if( (!Page.IsPostBack && this.PopulateOnLoad) || this.IsDirtyData)
            {
                this.Fill();
                this.IsDirtyData = false;
            }            
            }

            public override void DataBind()
            {
                  base.DataBind(); /************ ERROR HERE WHEN BINDING! ***********************/

                  //create new list item
                  if (this.IncludeExtraItem)
                  {
                        ListItem newItem = new ListItem();
                        newItem.Text = this.ExtraItemText;
                        newItem.Value = this.ExtraItemValue;
                        newItem.Selected = false;

                        //add list item to specified position
                        if((this.ExtraItemPosition == ExtraItemPosition.Top))
                        {
                              this.Items.Insert(0,newItem);
                        }
                        else if((ExtraItemPosition == ExtraItemPosition.Bottom))
                        {
                              this.Items.Add(newItem);
                        }
                  }

                  // now select the default item
                  if(this.InitialValue.ToString().Length > 0)
                  {
                        foreach (ListItem listItem in this.Items)
                        {
                              if(listItem.Value == InitialValue)
                              {
                                    listItem.Selected = true;
                                    break;
                              }
                        }
                  }
                  else
                  {
                        this.SelectedIndex = 0;
                  }
            }
            
            #endregion

            #region Properties

            [Description("If you set this value to true before the Load event occours then the control will reload its self."),Category("Loading")]
            public bool IsDirtyData
        {
            get
            {
                if(this.ViewState["IsDirtyData"] == null) this.ViewState["IsDirtyData"] = false;
                return (bool)this.ViewState["IsDirtyData"];
            }
            set
            {
                this.ViewState["IsDirtyData"] = value;
            }
        }            
            [Description("If you set this value to true then this control will pre-populate itself when it loads."),Category("Loading")]
        public bool PopulateOnLoad
        {
            get
            {
                if(this.ViewState["PopulateOnLoad"] == null) this.ViewState["PopulateOnLoad"] = true;
                return (bool)this.ViewState["PopulateOnLoad"];
            }
            set
            {
                this.ViewState["PopulateOnLoad"] = value;
            }
        }
            [Description("The value of the initially selected item"),Category("Data")]
            public string InitialValue
            {
                  get
                  {
                        if(this.ViewState["InitialValue"] == null)
                        {
                              this.ViewState["InitialValue"] = string.Empty;
                        }
                        return (string)this.ViewState["InitialValue"];
                  }

                  set
                  {
                        this.ViewState["InitialValue"] = value;
                  }
            }

            [Description("bool:  Include extra item in list?"),Category("Extra")]
            public bool IncludeExtraItem
            {
                  get
                  {
                        if(this.ViewState["IncludeExtraItem"]==null)
                        {
                              this.ViewState["IncludeExtraItem"] = false;
                        }
                        return (bool) this.ViewState["IncludeExtraItem"];
                  }
                  set
                  {
                        this.ViewState["IncludeExtraItem"] = value;
                  }
            }

            [Description("bool:  Should the extra item always been shown at the top of the list"),Category("Extra")]
            public ExtraItemPosition ExtraItemPosition
            {
                  get
                  {
                        if(this.ViewState["ExtraItemPosition"]==null)
                        {
                              this.ViewState["ExtraItemPosition"] = ExtraItemPosition.Top;
                        }
                        return (ExtraItemPosition) this.ViewState["ExtraItemPosition"];
                  }
                  set
                  {
                        this.ViewState["ExtraItemPosition"] = value;
                  }
            }

            [Description("string:  The text string displayed for extra item"),Category("Extra")]
            public string ExtraItemText
            {
                  get
                  {
                        if(this.ViewState["ExtraItemText"]==null)
                        {
                              this.ViewState["ExtraItemText"] = string.Empty;
                        }
                        return (string) this.ViewState["ExtraItemText"];
                  }
                  set
                  {
                        this.ViewState["ExtraItemText"] = value;
                  }
            }            

            [Description("string:  The value used for the extra item"),Category("Extra")]
            public string ExtraItemValue
            {
                  get
                  {
                        if(this.ViewState["ExtraItemText"]==null)
                        {
                              this.ViewState["ExtraItemText"] = string.Empty;
                        }
                        return (string) this.ViewState["ExtraItemText"];
                  }
                  set
                  {
                        this.ViewState["ExtraItemText"] = value;
                  }
            }      
      
            #endregion

      }
}

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