Question

我有一个包含数据库表数据的下拉列表，我想在另一个表中插入此ddl + 2 texbox字段。插入工作但总是先插入默认的dropdownList。我失踪了吗？

 protected void Page_Load(object sender, EventArgs e)
            {


                string connectionString = cs.getConnection();
                string query = "SELECT Id, NAME FROM PROFITCATEGORIES";
                using (SqlConnection myConnection = new SqlConnection(connectionString))
                {
                    myConnection.Open();
                    SqlCommand command = new SqlCommand(query, myConnection);
                    using (SqlDataReader rdr = command.ExecuteReader())
                    {

                        DropDownListCategory.DataSource = rdr;
                        DropDownListCategory.DataTextField = "Name";
                        DropDownListCategory.DataValueField = "ID";
                        DropDownListCategory.DataBind();

                    }
                }

            }

            protected void ButtonSave_Click(object sender, EventArgs e)
            {
                if (String.IsNullOrWhiteSpace(TextBoxValue.Text))
                    return;
                string connectionString = cs.getConnection();
                string insertSql = "INSERT INTO profits(Value,DateCreate,IdCategory,IdUser) VALUES(@Value, @DateCreate,@CategoryId,@UserId)";

                using (SqlConnection myConnection = new SqlConnection(connectionString))
                {
                    myConnection.Open();
                    SqlCommand command = new SqlCommand(insertSql, myConnection);
                    //параметризация се прави тук за да се избегне SQL Injection
                    command.Parameters.AddWithValue("@Value", TextBoxValue.Text);
                    command.Parameters.AddWithValue("@DateCreate", TextBoxData.Text);
                    command.Parameters.AddWithValue("@CategoryId", DropDownListCategory.SelectedValue);
                    command.Parameters.AddWithValue("@UserId", cui.getCurrentId());
                    command.ExecuteNonQuery();
                    //пренасочваме заявката към същата страница за да се видят новите резултати и да се избегне проблем с дублиране на инсерт при рефреш на страницата
                    Response.Redirect("~/Profit.aspx");
                    myConnection.Close();
                }
                TextBoxValue.Text = string.Empty;

            }

Answer 1

您在每次加载页面时重新绑定列表。将数据绑定代码包装在if (!IsPostBack)块中。

protected void Page_Load(object sender, EventArgs e)
{
   if (!IsPostBack)
   {
      // Bind the list here...
   }
}

Answer 2

每次按下asp：按钮都会重新加载页面，并且page_load方法中的代码会再次初始化。这就是默认项目始终插入数据库的原因。

将它放在page_load中的代码中：（if（！Page.IsPostback））

 protected void Page_Load(object sender, EventArgs e)
            { 

               if (!Page.isPostback)
                {
                string connectionString = cs.getConnection();
                string query = "SELECT Id, NAME FROM PROFITCATEGORIES";
                using (SqlConnection myConnection = new SqlConnection(connectionString))
                {
                    myConnection.Open();
                    SqlCommand command = new SqlCommand(query, myConnection);
                    using (SqlDataReader rdr = command.ExecuteReader())
                    {

                        DropDownListCategory.DataSource = rdr;
                        DropDownListCategory.DataTextField = "Name";
                        DropDownListCategory.DataValueField = "ID";
                        DropDownListCategory.DataBind();

                    }
                }
              }

            }

Answer 3

使用AppendDataBoundItems属性并将其设置为true，并仅在PostBack上绑定：

How Do I Add an Additional Item To a Databound DropDownList Control in ASP.NET?

ListControl.AppendDataBoundItems Property

dropdownlist始终插入默认值

3 个答案: