我想创建一个连接到数据库来执行操作的winform。它必须在打开时连接，然后根据用户点击的内容进行查询。我不是100％确定在加载时打开连接的最佳方法是什么，并且可以从所有不同的类访问该连接。我已经进行了一次测试运行以使连接工作，当用户单击按钮然后进行查询时打开数据库连接但是我想将数据库连接的开头移动到InitializeComponent（）部分然后从组件移动只需要调用已经建立的连接。
我已经设置了它，以便它根据具体情况运行，但是有更好的方法吗？我只是按照你能/应该的方式做到这一点？
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的
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);
}
}
}
}
queries.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;
}
}
}
答案 0 :(得分：0)
打开时必须连接，然后根据内容进行连接 用户点击，进行查询。 ... 我已经设置了它，以便它根据具体情况运行但是有一个 更好的方法吗？
绝对更好的方法。 不 在表单加载时打开连接，并保持打开状态。
您应始终遵循的经验法则是仅在需要时打开连接，并在完成使用后立即关闭。这意味着在实践中，在您需要运行查询之前不要打开它，尽可能接近实际的查询执行，然后在查询完成后立即关闭连接。
我不是100％确定在什么时候打开连接的最佳方法 它加载并使所有连接都可以访问 不同的班级
您所询问的是如何设计您的应用程序，您将获得的常见答案是使用n层设计。您应该阅读multitier architectures。