Question

当我打开表单时，它会通过绑定源自动加载数据库。有一个按钮可以按文本框中的值更改数据还有一个取消这些更改的按钮（如果您在文本框中输入值并按取消它将恢复为原始数据。

我不知道如何编码取消按钮，我已成功完成其他所有操作

我目前的更改代码（编辑:)是：

    using System;
    using System.Collections.Generic;
    using System.ComponentModel;
    using System.Data;
    using System.Drawing;
    using System.Linq;
    using System.Text;
    using System.Windows.Forms;
    using System.Data.OleDb;


    namespace Eastern_Property_Owners_Club

{

public partial class Club_Record_Maintenance : Form
{
    private OleDbConnection dbConn;     // Connection object
    private OleDbCommand dbCmd;         // Command object

    private string sConnection;
    private string sql;

    public Club_Record_Maintenance()
    {

        InitializeComponent();
        try
        {
            // Construct an object of the OleDbConnection class
            // to store the connection string representing
            // the type of data provider (database) and the source (actual db).

            //string ConnStr = @"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=D:\abc.mdb;Jet OLEDB:Database Password=password";

            //OleDbConnection MyConn = new OleDbConnection(ConnStr);



            // sConnection = "Provider = Microsoft.Jet.OLEDB.4.0;" + "Data Source = Student.mdb";


            sConnection = "Provider = Microsoft.Jet.OLEDB.4.0;" + "Data Source = Eastern_Property_Maintenance.mdb";
            dbConn = new OleDbConnection(sConnection);

            dbConn = new OleDbConnection(sConnection);
            dbConn.Open();

        }
        catch (System.Exception exc)
        {

            MessageBox.Show(exc.Message);
            return;
        }
    }

    private void button3_Click(object sender, EventArgs e)
    {
        //exits and goes to main menu
        MainMenu newForm = new MainMenu();
        newForm.Show();
        this.Close();
    }

    private void Club_Record_Maintenance_Load(object sender, EventArgs e)
    {
        // TODO: This line of code loads data into the 'eastern_Property_MaintenanceDataSet2.Club' table. You can move, or remove it, as needed.
        this.clubTableAdapter.Fill(this.eastern_Property_MaintenanceDataSet2.Club);

    }

    private void button1_Click(object sender, EventArgs e)
    {

        try
        {
            //declaring value to textboxes
            string Name = txtName.Text;
            string Address = txtAddress.Text;
            string Phone = txtPhone.Text;

            //declaring parameters in the SQL code
            //Field[Name] = whatever is in txtName.Text and so on
            //-----
            //adds values from the textboxes into the database
            sql = " UPDATE Club SET "
                    + " CompanyName = @Name"
                    + ","
                    + " CompanyAddress = @Address"
                    + ","
                    + " CompanyPhone = @Phone"
                    + " WHERE CompanyName = @Name; ";
            dbCmd = new OleDbCommand(sql, dbConn);

            //adding the perameters to ever place-holder in my sql

            dbCmd.Parameters.AddWithValue("@Name", txtName.Text);
            dbCmd.Parameters.AddWithValue("@Address", txtAddress.Text);
            dbCmd.Parameters.AddWithValue("@Phone", txtPhone.Text);

            // Execute query
            dbCmd.ExecuteNonQuery();
        }
        catch (System.Exception exc)
        {
            MessageBox.Show(exc.Message);
            return;
        }
        //a message to show the button has worked
        MessageBox.Show("Club has been Changed! \nRefresh the content by going back to the Main Menu");
    }

    private void btnCancel_Click(object sender, EventArgs e)
    {

        }
       }
    }

它工作正常，但我不知道如何编码取消按钮。

Answer 1

创建三个全局变量并将bool初始化为false以在检索数据时存储数据库中的值检查数据检索方法中的bool，如下所示并存储值。

if (!oldValues)
{
    // your code to store values from the database when the data is retrieved for the first time
    // change oldValues to true
}

因此，当进行更改并将其存储在数据库中时，这些全局变量将包含旧值。用户按下取消您使用这些变量来使用更新查询撤消更改，就像您在更新中使用的那样，但现在在取消按钮单击事件处理程序上...您还必须再次将bool更改为false，这样数据时再次检索它会将变量中的值存储为旧值。

编辑：

在表单加载事件中执行此操作：

bool oldValues = false; // that means there are not old values stored

制作这些全局变量：

string oldName;
string oldAddress; 
string oldPhone;

现在添加一个名为Add Record Button的按钮，并在单击时执行此操作：

if (!oldValues) //Checks that there are no old Values stored already
{
    if (txtName.Text != "") // handles the case if you have allowed nulls in this field
    {
        oldName = txtName.Text;
    }
    if (txtAddress.Text != "") // handles the case if you have allowed nulls in this field
    {
        oldAddress = txtAddress.Text;
    }
    if (txtPhone.Text != "") // handles the case if you have allowed nulls in this field
    {
        oldPhone = txtPhone.Text;
    }
    oldValues = true; // change to true so that program knows that there are old values stored
    txtName.Clear(); // Clear all text boxes on form so that user can enter new data
    txtAddress.Clear();
    txtPhone.Clear();
}

在“取消”按钮上执行此操作：

if (oldValues) // Check if old values are stored
{
    if (oldName != "") // check if its not an empty string
    {
        txtName.Text = oldName;
    }
    else // if it is a empty string then Clear the text box
        txtName.Clear();
    if (oldAddress != "")
    {
         txtAddress.Text = oldAddress;
    }
    else
        txtAddress.Clear();
    if (oldPhone != "")
    {
        txtPhone.Text = oldPhone;
    }
    else
        txtPhone.Clear();
    oldValues = false; // change the oldValues flag to false so that old values can be stored again...
}

如何使用按钮取消更改

1 个答案:

编辑：