Conflict in executing an event in Default page and another event in Master page

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C#

ASP.NET

WebForms

I have a ASP.NET Web Form Project, in the master page I have a button(searchButton), I wrote a code in searchButton_Click event, after clicking on "Go" button (also if user types something in the textbox and press Enter key), user will be redirected to another page(FrmSearchResult.aspx)

    public partial class Site1 : System.Web.UI.MasterPage
    {
        protected void Page_Load(object sender, EventArgs e)
        {
        }

        protected void searchButton_Click(object sender, EventArgs e)
        {
            Session["nameA"] = searchText.Text;
            Response.Redirect("FrmSearchResult.aspx");
            Session.RemoveAll();
        }
    }
}

I also have Default.aspx page which has mentioned master page!
In the default page I have a textbox (searchUniTextBox), and I implemented a code in searchUniTextBox_ValueChanged event!

protected void searchUniTextBox_ValueChanged(object sender, EventArgs e)
       {
           string searchUni = searchUniTextBox.Text.ToLower();
           string[] uniItem = new string[CheckBoxList1.Items.Count];
           for (int i = 0; i < CheckBoxList1.Items.Count; i++)
           {
               if (CheckBoxList1.Items[i].Text.ToLower().Contains(searchUni))
                   CheckBoxList1.Items[i].Selected = true;
           }
       }

But the problem is that whenever user presses Enter key, this event (searchUniTextBox_ValueChanged) executes, and immediately after that searchButton_Click in the master page executes!!!!!
I do not how I can prevent executing searchButton_Click event in the master page, when searchUniTextBox_ValueChanged event fires??
Thank you so much