ASP.NET enum dropdownlist validation

Question

I have got a enum

public enum TypeDesc
{
[Description("Please Specify")]
PleaseSpecify,
Auckland,
Wellington,
[Description("Palmerston North")]
PalmerstonNorth,
Christchurch
}

I am binding this enum to drop down list using the following code on page_Load

protected void Page_Load(object sender, EventArgs e)
        {
            if (TypeDropDownList.Items.Count == 0)
            {
                foreach (TypeDesc newPatient in EnumToDropDown.EnumToList<TypeDesc>())
                {
                 TypeDropDownList.Items.Add(EnumToDropDown.GetEnumDescription(newPatient));
                }
            }
        }

public static string GetEnumDescription(Enum value)
        {
            FieldInfo fi = value.GetType().GetField(value.ToString());

            DescriptionAttribute[] attributes =
                (DescriptionAttribute[])fi.GetCustomAttributes(typeof(DescriptionAttribute), false);

            if (attributes != null && attributes.Length > 0)
                return attributes[0].Description;
            else
                return value.ToString();
        }

        public static IEnumerable<T> EnumToList<T>()
        {
            Type enumType = typeof(T);

            // Can't use generic type constraints on value types,
            // so have to do check like this
            if (enumType.BaseType != typeof(Enum))
                throw new ArgumentException("T must be of type System.Enum");

            Array enumValArray = Enum.GetValues(enumType);
            List<T> enumValList = new List<T>(enumValArray.Length);

            foreach (int val in enumValArray)
            {
                enumValList.Add((T)Enum.Parse(enumType, val.ToString()));
            }

            return enumValList;
        }

and my aspx page use the following code to validate

            <asp:DropDownList ID="TypeDropDownList" runat="server" >
            </asp:DropDownList>
            <asp:RequiredFieldValidator ID="TypeRequiredValidator" runat="server" ControlToValidate="TypeDropDownList" ErrorMessage="Please Select a City" Text="<img src='Styles/images/Exclamation.gif' />"
                ValidationGroup="city"></asp:RequiredFieldValidator>

But my validation is accepting "Please Specify" as city name. I want to stop user to submit if the city is not selected.

tsukimi · Accepted Answer · 2012-06-29 04:03:47Z

2

Add a please specify before adding the enum items.

 TypeDropDownList.Items.Add("Please Specify","");
 foreach (TypeDesc newPatient in EnumToDropDown.EnumToList<TypeDesc>())
 {
    TypeDropDownList.Items.Add(EnumToDropDown.GetEnumDescription(newPatient), newPatient.ToString());
 }

Remove "Please Specify" from the enum

edited Jun 29, 2012 at 4:03

answered Jun 29, 2012 at 2:56

tsukimi

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4 Comments

KillerGearz Over a year ago

But I am saving my enum value as tinyint in my database. If I remove "Please Specify" from enum it will save 0 for Auckland in my database and I don't want that

tsukimi Over a year ago

well you can start the enum from 1 Auckland=1

KillerGearz Over a year ago

I did that it works this way for all values except "Palmerston North". visual studio through as Jscript error for validator given below:Microsoft JScript runtime error: Sys.WebForms.PageRequestManagerServerErrorException: 'TypeDropDownList' has a SelectedValue which is invalid because it does not exist in the list of items. Parameter name: value

KillerGearz Over a year ago

Thanks for that I sorted it out.... our code is almost the same.... please refer to my answer...... thanks for the help

Polity · Accepted Answer · 2012-06-29 03:12:39Z

0

DropDownList can bind to a Value and Text property when explicitly specified. When the value for an item is null, this will be picked up by your validator.

<asp:DropDownList ID="TypeDropDownList" runat="server" DataTextField="Text" DataValueField="Value" ></asp:DropDownList>

and when adding items:

foreach (TypeDesc newPatient in EnumToDropDown.EnumToList<TypeDesc>())
{
   string text = EnumToDropDown.GetEnumDescription(newPatient)),
   TypeDropDownList.Items.Add(new
   {
       Text = text,
       Value = text == "Please specify" ? null : text // should be replaced with a clean solution
   }
}

edited Jun 29, 2012 at 3:12

answered Jun 29, 2012 at 2:57

Polity

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4 Comments

tsukimi Over a year ago

What would be a cleaner solution?

KillerGearz Over a year ago

didn't work through a Jscript error: Microsoft JScript runtime error: Sys.WebForms.PageRequestManagerServerErrorException: 'TypeDropDownList' has a SelectedValue which is invalid because it does not exist in the list of items. Parameter name: value

Polity Over a year ago

@tsukimi - Assign an attribute like System.ComponentModel.DataAnnotations.KeyAttribute and when set, use that value as the value

Polity Over a year ago

@ArunKumar - Sorry, you have to use an empty string.

KillerGearz · Accepted Answer · 2012-06-29 03:58:16Z

I sorted it out I used the following code

if (TypeDropDownList.Items.Count == 0)
            {
                foreach (TypeDesc newPatient in EnumToDropDown.EnumToList<TypeDesc>())
                {
                    string text = EnumToDropDown.GetEnumDescription(newPatient);

                    TypeDropDownList.Items.Add(new ListItem(text, newPatient.ToString()));
                }
            }

and the validator as

<asp:RequiredFieldValidator ID="TypeRequiredValidator" runat="server" ControlToValidate="TypeDropDownList"
                InitialValue="PleaseSpecify" ErrorMessage="Please Select a City" Text="<img src='Styles/images/Exclamation.gif' />"
                ValidationGroup="city"></asp:RequiredFieldValidator>

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