小编Ozz*_*490的帖子

任何有关这方面的帮助将不胜感激.每当我运行我的程序时,我得到一个NullReferenceException未被用户代码处理.

因此,当我启动程序时,我会看到一个表单,我应该从名单列表中进行选择,并能够更新详细信息或删除它们,但下拉列表中没有任何内容.

我得到空引用:

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

这是CS文件中的选择按钮:

protected void selectButton_Click(object sender, EventArgs e)
{
    // Declare objects
    SqlConnection conn;
    SqlCommand comm;
    SqlDataReader reader;
    // Read the connection string from Web.config
    string connectionString =
        ConfigurationManager.ConnectionStrings[
        "HelpDesk"].ConnectionString;
    // Initialize connection
    conn = new SqlConnection(connectionString);
    // Create command
    comm = new SqlCommand(
        "SELECT FirstName, LastName, Username, Address, City, County, Post Code, " +
        "HomePhone, Extension, MobilePhone FROM Employees " +
        "WHERE EmployeeID = @EmployeeID", conn);
    // Add command parameters
    comm.Parameters.Add("@EmployeeID", System.Data.SqlDbType.Int);
    comm.Parameters["@EmployeeID"].Value = …