How do I fix error await operator can only be used within an async method?

Question

_{Thursday, January 9, 2020 8:36 PM}

My code behind for GetCasesButton_Click have an error which I am unable to fix. I need help.
The error is on await CandidateCaseController.GetNextBAtchNumber() line.

It says **The 'await' operator can only be used within an async method. Consider marking this method with the 'async' modifier and changing its return type to 'Task'. **

Please help fix this.

Here is the code behind for GetCasesButton_Click

protected void GetCasesButton_Click(object sender, EventArgs e)
 {
 #region Required Field Validation
    if (CaseNumbersTextBox.Text.Length < 1)
    {
       string myStringVariable = "Case number textbox cannot be empty.";
       ClientScript.RegisterStartupScript(this.GetType(), "myalert", "alert('" + myStringVariable + "');", true);
     }
        if (RequestorDropDownList.SelectedItem.Value !=null)
        {
            ListItem requestorItem = new ListItem();
            requestorItem = (ListItem)RequestorDropDownList.SelectedItem;
        }
            
        if (ReasonDropDownList.SelectedItem.Value !=null)
        {
           ListItem reasonItem = new ListItem();
           reasonItem = (ListItem)ReasonDropDownList.SelectedItem;
        }
        #region Parse case number entries
        string userEnteredCaseNumbers = CaseNumbersTextBox.Text;
        userEnteredCaseNumbers = userEnteredCaseNumbers.Replace("\r", ",");
        userEnteredCaseNumbers = userEnteredCaseNumbers.Replace("\n", ",");
        
        while (userEnteredCaseNumbers.Contains(",,"))
            userEnteredCaseNumbers = userEnteredCaseNumbers.Replace(",,", ",");
            List<string> userEnteredCaseNumberList = new List<string>();
            userEnteredCaseNumberList = userEnteredCaseNumbers.Split(',').Where(x => x.Length > 0).ToList();
            userEnteredCaseNumberList = userEnteredCaseNumberList.Select(s => s.Trim()).ToList();
            #endregion
        try
        {
          #region Get Batch Number
          int newBatchNumber = await CandidateCaseController.GetNextBatchNumber();
          #endregion
          #region Insert entered case numbers in database
          foreach(string caseNumber in userEnteredCaseNumberList)
          {
             EditCandidateCaseModel newCandidate = new EditCandidateCaseModel();
             newCandidate.CaseNbr = caseNumber;
             //newCandidate.RequestorInfoID = requestorItem.Value;
             //newCandidate.RequestorInfoID = (ListItem)RequestorDropDownList.SelectedItem.Value;
             //newCandidate.ReasonID = requestorItem.Value;
             newCandidate.BatchNumber = newBatchNumber;
             newCandidate.EntryStaffUserName = this._loggedInUserName;
             await CandidateCaseController.PostCandidate(newCandidate);
          }

          #endregion
          }
            catch (Exception ex)
            {
               string errorMsg = string.Format("An error has occured in {0}. \nException:\n{1}", "GetCasesButton_Click()", ex.Message);
                MessageBox.Show(errorMsg, "Application Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                ClientScript.RegisterStartupScript(this.GetType(), "myalert", "alert('" + errorMsg + "');", true);
                return;
            }
}

Here is the aspx code for the button

<asp:Button ID="GetCasesButton" runat="server" Text="Get Cases" Font-Size="8.25"
    BackColor="RoyalBlue" ForeColor="White" Height="24px" Width="74px"
    OnClick="GetCasesButton_Click" />

All replies (3)

_{Thursday, January 9, 2020 8:40 PM ✅Answered}

Hello,

This is the solution

protected async void GetCasesButton_Click(object sender, EventArgs e)

Please remember to mark the replies as answers if they help and unmarked them if they provide no help, this will help others who are looking for solutions to the same or similar problem. Contact via my Twitter (Karen Payne) or Facebook (Karen Payne) via my MSDN profile but will not answer coding question on either.

NuGet BaseConnectionLibrary for database connections.

StackOverFlow

_{Thursday, January 9, 2020 11:19 PM}

Hello,

Did adding async resolve your issue?

Please remember to mark the replies as answers if they help and unmarked them if they provide no help, this will help others who are looking for solutions to the same or similar problem. Contact via my Twitter (Karen Payne) or Facebook (Karen Payne) via my MSDN profile but will not answer coding question on either.

NuGet BaseConnectionLibrary for database connections.

StackOverFlow

_{Friday, January 10, 2020 2:16 AM}

Hi,

Thank you for posting here.

Karen's answer is correct, we can only use await in an async method.

You can read the Microsoft documentation to learn more about asynchronous programming, it's really useful.

Asynchronous programming with async and await

await operator (C# reference)

Best Regards,

Timon

MSDN Community Support
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