Display Text in text box according to text entered in another text box

Question

I am writing a web application in asp.net. I have two text box one field is for txtEmployeeID and the other field is for txtEmployeeName. I set the EmployeeName textbox to readonly in the Page_Load event. In my program, I have connected to my database and set up my stored procedure. What I want right now is when I typed a ID in my EmployeeID textbox, the corresponding EmployeeName textbox should displayed in the employee's name in that textbox.

For example. In my db, I have

employeeID: 000123 
employeeName: Jimmy

If I type 000123 in my txtEmployeeID, the name Jimmy will show in txtEmployeeName.

I was thinking to use JavaScript to accomplish this. This is what I was thinking but all it does is copy the text in one text box and display the same text in another textbox.

     function Text() {
        var txt1 = document.getElementById('<%= txtEmployeeID.ClientID %>').value;
        document.getElementById('<%= txtEmployeeName.ClientID %>').value = txt1;

     }

HTML Code:

<asp:TemplateField HeaderText="Employee ID">
       <EditItemTemplate>
              <asp:TextBox ID="txtEmployeeID" runat="server" Text='<%#Bind("Employee_ID") %>'
                Width="90px"></asp:TextBox>
       </EditItemTemplate>
       <ItemTemplate>
            <asp:Label ID="lblEmployeeName" runat="server" CssClass="GridInput" Text='<%#Bind("Employee_Name") %>'
                 Width="90px"></asp:Label>
        </ItemTemplate>
</asp:TemplateField>

Answer 1

If you want to use the OnTextChange event, you can do so like this;

<asp:UpdatePanel ID="udpEmployee" runat="server">
    <ContentTemplate>
        <asp:TextBox ID="txtEmployeeID" runat="server" AutoPostBack="true" OnTextChanged="txtEmployeeID_TextChanged"></asp:TextBox>
        <asp:TextBox ID="txtEmployeeName" runat="server" ReadOnly="true"></asp:TextBox>
    </ContentTemplate>
</asp:UpdatePanel>

And in code behind;

protected void txtEmployeeID_TextChanged(object sender, EventArgs e)
    {
        //get employee name from DB
        string employeeName = GetEmployeeName(txtEmployeeID.Text);

        //set employee name on txtEmployeeName
        txtEmployeeName.Text = employeeName;
    }

I'm not sure how you are connecting to your DB so unable to provide an example of getting the value.