How do I make a method populate a dropdownlist?

Question

0.00/5 (No votes)

See more:

I am not sure how to change my method so that it populates RequestorDropDownList when the page loads.

A user will only be able to select one name from the the RequestorDropDownList.

Please help.

What I have tried:

Here is my method.

C#

public async void RequestorDropDownList()
        {
            List<GetRequestorInfoModel> requestors = new List<GetRequestorInfoModel>();
            RequestorDropDownList.Items.Clear();
            RequestorUpdateDropDownList.Items.Clear();

            try
            {
                requestors = await FTACaseReset.Controllers.RequestorInfoController.GetAllRequestorInfoes();
                requestors = requestors.OrderBy(x => x.DisplayName).ToList();

                #region Populate RequestorDropDownList
                DropDownListItem firstRequestor = new DropDownListItem();
                firstRequestor.Text = "<-Please select Requestor->";
                firstRequestor.Value = 0;
                RequestorDropDownList.Items.Add(firstRequestor);

                for (int i = 0; i < requestors.Count; i++)
                {
                    DropDownItem item = new DropDownItem();
                    item.Text = requestors[i].DisplayName;
                    item.Value = requestors[i].RequestorInfoID;
                    RequestorDropDownList.Items.Add(item);
                }

                if (RequestorDropDownList.Items.Count > 0)
                    RequestorDropDownList.SelectedIndex = 0;
                #endregion

                #region Populate RequestorUpdateDropDownList
                for (int i = 0; i < requestors.Count; i++)
                {
                    DropDownItem item = new DropDownItem();
                    item.Text = requestors[i].DisplayName;
                    item.Value = requestors[i].RequestorInfoID;
                    RequestorDropDownList.Items.Add(item);
                }
                #endregion
            }
            catch (Exception ex)
            {
                string errorMsg = string.Format("An error has occured in {0}. \nException:\n{1}", "PopulateRequestorDropDownList()", ex.Message);
                MessageBox.Show(errorMsg, "Application Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

Posted 19-Dec-19 7:23am

Member 11403304

Updated 19-Dec-19 7:31am

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Richard Deeming · Accepted Answer · 2019-12-19T07:32:00

You're updating two lists, so make your method async Task instead of async void, and use Page.RegisterAsyncTask:

C#

public async Task RequestorDropDownList() { ... }

public void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        Page.RegisterAsyncTask(new PageAsyncTask(RequestorDropDownList));
    }
}

NB: MessageBox.Show won't work in an ASP.NET application. Your code is running on the server, so the message would pop up on the server, where nobody would ever see it.

It might appear to work when you're debugging the application in Visual Studio. But that's only because, in that specific case, the server and the client are the same computer.

NB2: You're currently adding the items to RequestorDropDownList in both loops. I suspect the second loop should be adding them to RequestorUpdateDropDownList.