C# NullReferenceException was unhandled by user code

This question already has an answer here:

What is a NullReferenceException, and how do I fix it? 33 answers

---

Put a breakpoint at:

comm.Parameters["@EmployeeID"].Value =
        employeesList.SelectedItem.Value;

When you run you program check the value of:

employeesList.SelectedItem

Most likely this will be null if no item has been selected. Try checking for a null value before using:

 if (employeesList.SelectedItem != null)
 {
comm.Parameters["@EmployeeID"].Value =
    employeesList.SelectedItem.Value;
 }
 else
 {
// Handle this case
 }

Hope this helps!

---

It doesn't look like you added any items to your dropdown list.

You have:

<p>
<asp:Label ID="dbErrorLabel" ForeColor="Red" runat="server" />
Select an employee to update:<br />
<asp:DropDownList ID="employeesList" runat="server" />
<asp:Button ID="selectButton" Text="Select" runat="server"
    onclick="selectButton_Click" />

But a dropdown list should have items like:

<asp:DropDownList ID="employeesList" runat="server">
    <asp:ListItem Text="Item 1" Value="1" Selected="true" />
    <asp:ListItem Text="Item 2" Value="2"/>
</asp:DropDownList>

---

First you have to fill your data in the drop down list from the table available in the database.

Sample Code: In Page_Load,

if (!IsPostBack)
{
   ddlName.DataSource=ds;
   ddlName.DataValueField="ID";
   ddlName.DataTextField="NAME";
   ddlName.DataBind();
}

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