我想创建一个连接到数据库来做事的winform。它必须在打开时连接，然后根据用户单击的内容进行查询。我不是 100% 确定最好的课程是在加载时打开连接并使该连接能够从所有不同的类访问。我已经进行了测试运行以使连接正常工作，当用户单击按钮然后进行查询时打开数据库连接，但我想将数据库连接的打开移动到 InitializeComponent() 部分，然后从组件只需调用已经建立的连接。
我已经进行了设置，以便逐案运行，但有没有更好的方法来做到这一点？我是这样做的，只有你可以/应该这样做？
这是测试
Form1.Designer.cs
namespace end_of_day
{
using System.Data.SqlClient;
partial class Form1
{
/// <summary>
/// Required designer variable.
/// </summary>
private System.ComponentModel.IContainer components = null;
/// <summary>
/// Clean up any resources being used.
/// </summary>
/// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
protected override void Dispose(bool disposing)
{
if (disposing && (components != null))
{
components.Dispose();
}
base.Dispose(disposing);
}
#region Windows Form Designer generated code
/// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()
{
this.button1 = new System.Windows.Forms.Button();
this.label1 = new System.Windows.Forms.Label();
this.button2 = new System.Windows.Forms.Button();
this.button3 = new System.Windows.Forms.Button();
this.button4 = new System.Windows.Forms.Button();
this.SuspendLayout();
//
// button1
//
this.button1.Location = new System.Drawing.Point(78, 411);
this.button1.Name = "button1";
this.button1.Size = new System.Drawing.Size(147, 64);
this.button1.TabIndex = 0;
this.button1.Text = "Test";
this.button1.UseVisualStyleBackColor = true;
this.button1.Click += new System.EventHandler(this.button1_Click);
//
// label1
//
this.label1.AutoSize = true;
this.label1.Location = new System.Drawing.Point(13, 13);
this.label1.Name = "label1";
this.label1.Size = new System.Drawing.Size(199, 13);
this.label1.TabIndex = 1;
this.label1.Text = "ERROR: didn\'t connect to the database.";
//
// button4
//
this.button4.Location = new System.Drawing.Point(78, 201);
this.button4.Name = "button4";
this.button4.Size = new System.Drawing.Size(147, 64);
this.button4.TabIndex = 4;
this.button4.Text = "Print Out of Stock";
this.button4.UseVisualStyleBackColor = true;
this.button4.Click += new System.EventHandler(this.button4_Click);
//
// Form1
//
this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
this.ClientSize = new System.Drawing.Size(306, 523);
this.Controls.Add(this.button4);
this.Controls.Add(this.button3);
this.Controls.Add(this.button2);
this.Controls.Add(this.label1);
this.Controls.Add(this.button1);
this.Name = "Form1";
this.Text = "End of day";
this.ResumeLayout(false);
this.PerformLayout();
}
#endregion
private System.Windows.Forms.Button button1;
private System.Windows.Forms.Label label1;
private System.Windows.Forms.Button button4;
// NOTE I NEED TO BE ABLE TO CHANGE THE LABEL FROM OTHER CLASSES FIX THIS SOMEHOW
}
}
Form1.cs
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
using System.Net.Mail;
namespace end_of_day
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
SqlConnection myConnection = queries.create_concection();
try
{
SqlDataReader myReader = null;
SqlCommand myCommand = new SqlCommand("SELECT TOP 100000 ItemName,Price,In_Stock,Vendor_Part_Num FROM Inventory",
myConnection);
myReader = myCommand.ExecuteReader();
String mess = "";
int i = 0;
while (myReader.Read())
{
if (i < 10)
{
mess += myReader["ItemName"].ToString();
mess += myReader["Price"].ToString();
mess += "\r\n";
}
i++;
}
}
catch (Exception er)
{
DialogResult dlgRes = MessageBox.Show(er.ToString(), "Error", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Question);
}
}
private void button4_Click(object sender, EventArgs e)
{
SqlConnection myConnection = queries.create_concection();
DialogResult dlgRes = MessageBox.Show("Exculde Videos?",
"Options",
MessageBoxButtons.YesNoCancel,
MessageBoxIcon.Question);
String SQL_op = "";
if (dlgRes == DialogResult.Yes)
{
SQL_op = "AND NOT Dept_ID = 'video'";
}
try
{
SqlDataReader myReader = null;
SqlCommand myCommand = new SqlCommand("SELECT TOP 100000 ItemName,Price,In_Stock,Vendor_Part_Num FROM Inventory WHERE In_Stock<1 AND NOT Dept_ID = '006' "+ SQL_op+" ORDER BY Dept_ID",
myConnection);
myReader = myCommand.ExecuteReader();
String mess = "";
int i = 0;
while (myReader.Read())
{
if (i < 10)
{
mess += myReader["ItemName"].ToString();
mess += myReader["Price"].ToString();
mess += "\r\n";
}
i++;
}
dlgRes = MessageBox.Show("Had " + i + "items including: \r\n" + mess,
"Confirm Document Close",
MessageBoxButtons.YesNoCancel,
MessageBoxIcon.Question);
}
catch (Exception er)
{
dlgRes = MessageBox.Show(er.ToString(), "Error", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Question);
}
}
}
}
查询.cs
using System;
using System.Collections.Generic;
using System.Xml;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.SqlClient;
using System.Web;
namespace end_of_day
{
public class queries
{
public static SqlConnection create_concection()
{
Boolean hasConection =true;
SqlConnection myConnection = new SqlConnection(
"Data Source=localhost\\SQLEXPRESS;" +
"Trusted_Connection=true;" +
"Initial Catalog=TESTDB; " +
"connection timeout=30"
);
try
{
myConnection.Open();
}
catch (Exception er)
{
hasConection = false;
DialogResult dlgRes = MessageBox.Show(er.ToString(), "Error", MessageBoxButtons.YesNoCancel, MessageBoxIcon.Question);
}
if (hasConection) {
// THIS SHOULD CHANGE THE LABEL OF THE MAIN FORM
//Form1 form = new Form1();
//form.MyMessage = "made it";
}
return myConnection;
}
}
}