reset (reload or refresh) DropDownList with protected void Button1_Click(object sender, EventArgs e)

Question

Hello Forum Members

I am trying to reset (reload or refresh) the values of the dropdownlist.

Here is the code in asp.net:

<asp:DropDownList

ID="ddlUsage1" runat="server"

AutoPostBack="true"

DataSourceID="DropDownDataSourceUsage1"

DataTextField="Usage1"

DataValueField="Usage1"

AppendDataBoundItems="true" Width="100px"

OnSelectedIndexChanged="ddlUsage1_SelectedIndexChanged">

<asp:ListItem Text="All Usage" Value=""></asp:ListItem>

</asp:DropDownList>

code behind:

protected void Button1_Click(object sender, EventArgs e)

{

ddlUsage1.Items.Clear(); --- this is the problem.

}

Instead of clear (), how can I reset (reload or refresh) the values of the dropdownlist?

I sincerely appreciate your help.

Answer 1

Hi @Cyber Learning ,

When there is any update on your data source, you can call DataBind() again to reload the data source. Here is simple example:

   protected void Button1_Click(object sender, EventArgs e)  
           {  
               string constr = ConfigurationManager.ConnectionStrings["conStr"].ToString();  
     
               using (SqlConnection conn = new SqlConnection(constr))  
               {  
                   string cmdString = "INSERT INTO dbo.DDLItems VALUES (5,'Item5','Value5')";  
                   conn.Open();  
                   using (SqlCommand comm = new SqlCommand(cmdString, conn))  
                   {  
                       comm.ExecuteNonQuery();  
                   }  
               }  
     
               ddlUsage1.DataBind();  
           }  

Result:

Best regards,
Xudong Peng

---

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Answer 2

Hello Xudong Peng

I apologize for not getting back to you sooner. I got pretty sick and now am recovering.

I would like to resume this question.

I have the clear button as follows:

<asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="CLEAR" />

I have the code behind as follows:

protected void Button1_Click(object sender, EventArgs e)
        {
            string constr = ConfigurationManager.ConnectionStrings["conStr"].ToString();
            using (SqlConnection conn = new SqlConnection(constr))
            {
                string cmdString = "INSERT INTO dbo.DDLItems VALUES (5,'Item5','Value5')";
                conn.Open();
                using (SqlCommand comm = new SqlCommand(cmdString, conn))
                {
                    comm.ExecuteNonQuery();
                }
            }
            ddlUsage1.DataBind();
        }

But, the button control still doesn't work.

Do you have other suggestions on what else I need to check?

Thank you.

Answer 3

Hello Xudong Peng

I ended up using javascript, and it is providing the same effect.

function ResetDropDownList()

Thank you again for your help.