Dynamically generating a DropdownLIst control from an array populating with Text and Values

Question

I am trying to bind a DropDownList control to various data store. In my case the data store are arrays file values and Item Texts.

This is a short example of my HTML:

 <asp:DropDownList ID="DropDownListDealCategory"  
                                          runat="server" 
                                          Height="25px" 
                                          Width="150px" 
                                          AutoPostBack="true"
                                          OnSelectedIndexChanged="DropDownListDealCategory_SelectedIndexChanged">
                            <asp:ListItem Selected="True" Value="0">-- Select Category --</asp:ListItem>
                            <asp:ListItem Value="10">Electronics</asp:ListItem>
                            <asp:ListItem Value="22">Computer</asp:ListItem>                               
                        </asp:DropDownList>

<asp:DropDownList ID="DropDownSubCategories" 
                                            runat="server" 
                                            Visible="false" 
                                            Height="25px" 
                                            Width="170px" 
                                            AutoPostBack="true"
                                            OnSelectedIndexChanged="DropDownSubCategories_SelectedIndexChanged">
                        </asp:DropDownList>

The code behind (C#) will dynamically generate a DropDownList control from two arrays.

    protected void DropDownDealCategory_SelectedIndexChanged(object sender, EventArgs e)
{
string[] Electronics = new[] { " Select Subcategory ", "Cameras and Photography", "Home Audio"};
string[] Computer = new[] {" Select Subcategory " "Laptops", "Monitors"};

if (DropDownListCategory.SelectedItem.Text == "Electronics")
    {
        DropDownSubCategories.DataSource = Electronics;
    }
 else if (DropDownListDealCategory.SelectedItem.Text == "Computer")
    {
        DropDownSubCategories.DataSource = Computer;
    }

DropDownSubCategories.DataBind();
    DropDownSubCategories.Visible = DropDownListCategory.SelectedItem.Text != " Select Category ";

So, till here everything is fine except that I need a categoryId for every item in DropDownSubCategories DropDownList control as well, otherwise I wouldn't be able to retrieve any product from an external database, since I need a name + categoryid in order to display a product description.

My question is, Is there any way to add two values ( one as a Value and the other as Item.Text ) to an array, so I can bind both to the DropDownList control ?

Thank you, any help or even an alternative suggestion will be appreciate it.

Blue Eyed Behemoth · Accepted Answer · 2016-05-25 19:15:46Z

2

Try using ListItems. Should look something like the following.

        var Electronics = new[]{
            new ListItem{ Value = "0", Text = " Select Subcategory "},
            new ListItem{ Value = "1", Text = "Cameras and Photography"},
            new ListItem{ Value = "2", Text = "Home Audio"},
        };

You may have to add the using.

using System.Web.UI.WebControls;

EDIT:

Try adding them this way:

DropDownSubCategories.Items.Clear();
DropDownSubCategories.Items.AddRange(Electronics);

Or if AddRange() Isn't a function, individually:

DropDownSubCategories.Items.Add(new ListItem{ Value = "2", Text = "Home Audio"});

And so on.

edited May 25, 2016 at 19:15

answered May 25, 2016 at 17:59

Blue Eyed Behemoth

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4 Comments

Tomas Jimenez Over a year ago

With this approach I get only a value for the Text.

Blue Eyed Behemoth Over a year ago

Because DataBind method binds values only if DataValueField property is set. If you set DataValueField property to "Value" before calling DataBind, your values will appear on the markup. You will also need to set DataTextField property to "Text". It is because data binding and adding items manually do not work in the same way. Databinding does not know the existence of type ListItem and generates markup by evaluating the items in the data source. Either that or just add them as Items

Blue Eyed Behemoth Over a year ago

@TomasJimenez Unfortunately I work with MVC so it's slightly different. You might have to play around with it.

Tomas Jimenez Over a year ago

Thanks a lot ! you got it !

espCoder · Accepted Answer · 2016-05-25 18:03:41Z

0

The Dictionary class is designed to store key/value pairs.

            Dictionary<int, string> Electronics = new Dictionary<int, string>() {

            {0, "Select Subcatagory" },
            {1, "Cameras and Photography" },
            {2, "Home Audio" }

        };

answered May 25, 2016 at 18:03

espCoder

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1 Comment

Tomas Jimenez Over a year ago

I have created a test Label (LabelCat) to see the result of both approaches, yours and the one suggested from "Blue Eyed Behemoth". LabelCat.Text = DropDownListSubCategories.SelectedValue; and I get this result [23, Amplifiers]. So, not really useful. Thanks for helping, though.

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