C# 如何将数据库中的数据显示到文本框中，并更新它

How to display data from database into textbox, and update it

提问by Ching

I can display my data in my textbox, dropdownlist after retrieve data from sql database, but when i proceed with my update button, the information edited in the textbox or dropdownlist wouldn't update into the database. I tried to remove the code in page load, and re-key in all the data manually, it can be update. All I want is retrieve data from database and display it in the textbox, and it can be update into the database after make some changes from the textbox. Can someone help me on this? Thanks.

从 sql 数据库中检索数据后，我可以在我的文本框、下拉列表中显示我的数据，但是当我继续执行更新按钮时，在文本框或下拉列表中编辑的信息不会更新到数据库中。我尝试删除页面加载中的代码，并手动重新输入所有数据，它可以更新。我想要的只是从数据库中检索数据并将其显示在文本框中，并且可以在从文本框中进行一些更改后将其更新到数据库中。有人可以帮助我吗？谢谢。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Configuration;
using System.Data;
public partial class UpdateCustomerDetails : System.Web.UI.Page
{

protected void Page_Load(object sender, EventArgs e)
{
    SqlConnection con1 = new SqlConnection("Data Source=USER-PC;Initial Catalog=webservice_database;Integrated Security=True");
    DataTable dt = new DataTable();
    con1.Open();
    SqlDataReader myReader = null;  
    SqlCommand myCommand = new SqlCommand("select * from customer_registration where username='" + Session["username"] + "'", con1);

    myReader = myCommand.ExecuteReader();

    while (myReader.Read())
    {
        TextBoxPassword.Text = (myReader["password"].ToString());
        TextBoxRPassword.Text = (myReader["retypepassword"].ToString());
        DropDownListGender.SelectedItem.Text = (myReader["gender"].ToString());
        DropDownListMonth.Text = (myReader["birth"].ToString());
        DropDownListYear.Text = (myReader["birth"].ToString());
        TextBoxAddress.Text = (myReader["address"].ToString());
        TextBoxCity.Text = (myReader["city"].ToString());
        DropDownListCountry.SelectedItem.Text = (myReader["country"].ToString());
        TextBoxPostcode.Text = (myReader["postcode"].ToString());
        TextBoxEmail.Text = (myReader["email"].ToString());
        TextBoxCarno.Text = (myReader["carno"].ToString());
    }
    con1.Close();
}
protected void Button1_Click(object sender, EventArgs e)
{
    SqlConnection con = new SqlConnection("Data Source=USER-PC;Initial Catalog=webservice_database;Integrated Security=True");
    SqlCommand cmd = new SqlCommand("UPDATE customer_registration SET password = @password, retypepassword = @retypepassword, gender = @gender, birth = @birth, address = @address, city = @city, country = @country, postcode = @postcode, email = @email, carno = @carno where username='" + Session["username"] + "'", con);
    con.Open();

    cmd.Parameters.AddWithValue("@password", TextBoxPassword.Text);
    cmd.Parameters.AddWithValue("@retypepassword", TextBoxRPassword.Text);
    cmd.Parameters.AddWithValue("@gender", DropDownListGender.Text);
    cmd.Parameters.AddWithValue("@birth", DropDownListDay.Text + DropDownListMonth.Text + DropDownListYear.Text);
    cmd.Parameters.AddWithValue("@address", TextBoxAddress.Text);
    cmd.Parameters.AddWithValue("@city", TextBoxCity.Text);
    cmd.Parameters.AddWithValue("@country", DropDownListCountry.Text);
    cmd.Parameters.AddWithValue("@postcode", TextBoxPostcode.Text);
    cmd.Parameters.AddWithValue("@email", TextBoxEmail.Text);
    cmd.Parameters.AddWithValue("@carno", TextBoxCarno.Text);

    cmd.ExecuteNonQuery();
    con.Close();
    if (IsPostBack)
    {
        Response.Redirect("UpdateSuccess.aspx");
    }
}

采纳答案by Kundan Singh Chouhan

Wrap your all statements in !IsPostBackcondition on page load.

!IsPostBack在页面加载时将所有语句包装在条件中。

protected void Page_Load(object sender, EventArgs e)
{
   if(!IsPostBack)
   {
      // all statements
   }
}

This will fix your issue.

这将解决您的问题。

回答by codingbiz

The answer is .IsPostBackas suggested by @Kundan Singh Chouhan. Just to add to it, move your code into a separate method from Page_Load

答案是.IsPostBack@Kundan Singh Chouhan 所建议的。只是为了添加它，将您的代码移动到与 Page_Load 不同的方法中

private void PopulateFields()
{
  using(SqlConnection con1 = new SqlConnection("Data Source=USER-PC;Initial Catalog=webservice_database;Integrated Security=True"))
  {
    DataTable dt = new DataTable();
    con1.Open();
    SqlDataReader myReader = null;  
    SqlCommand myCommand = new SqlCommand("select * from customer_registration where username='" + Session["username"] + "'", con1);

    myReader = myCommand.ExecuteReader();

    while (myReader.Read())
    {
        TextBoxPassword.Text = (myReader["password"].ToString());
        TextBoxRPassword.Text = (myReader["retypepassword"].ToString());
        DropDownListGender.SelectedItem.Text = (myReader["gender"].ToString());
        DropDownListMonth.Text = (myReader["birth"].ToString());
        DropDownListYear.Text = (myReader["birth"].ToString());
        TextBoxAddress.Text = (myReader["address"].ToString());
        TextBoxCity.Text = (myReader["city"].ToString());
        DropDownListCountry.SelectedItem.Text = (myReader["country"].ToString());
        TextBoxPostcode.Text = (myReader["postcode"].ToString());
        TextBoxEmail.Text = (myReader["email"].ToString());
        TextBoxCarno.Text = (myReader["carno"].ToString());
    }
    con1.Close();
  }//end using
}

Then call it in your Page_Load

然后在你的 Page_Load 中调用它

protected void Page_Load(object sender, EventArgs e)
{

    if(!Page.IsPostBack)
    {
       PopulateFields();
    }
}

回答by Shailendra Mishra

protected void Page_Load(object sender, EventArgs e)

    {

        DropDownTitle();
    }


protected void DropDownTitle()
{
    if (!Page.IsPostBack)
    {

        string connection = System.Configuration.ConfigurationManager.ConnectionStrings["AuzineConnection"].ConnectionString;

        string selectSQL = "select DISTINCT ForumTitlesID,ForumTitles from ForumTtitle";
        SqlConnection con = new SqlConnection(connection);
        SqlCommand cmd = new SqlCommand(selectSQL, con);
        SqlDataReader reader;
        try
        {

            ListItem newItem = new ListItem();
            newItem.Text = "Select";
            newItem.Value = "0";
            ForumTitleList.Items.Add(newItem);
            con.Open();
            reader = cmd.ExecuteReader();



            while (reader.Read())
            {
                ListItem newItem1 = new ListItem();
                newItem1.Text = reader["ForumTitles"].ToString();
                newItem1.Value = reader["ForumTitlesID"].ToString();
                ForumTitleList.Items.Add(newItem1);



            }
            reader.Close();
            reader.Dispose();
            con.Close();
            con.Dispose();
            cmd.Dispose();


        }
        catch (Exception ex)
        {
            Response.Write(ex.Message);
        }

    }
}

回答by John Wilson

Populate the text box values in the Page Init event as opposed to using the Postback.

在 Page Init 事件中填充文本框值，而不是使用回发。

protected void Page_Init(object sender, EventArgs e)
{
    DropDownTitle();
}