namespace 第15章_数据访问技术
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
SqlConnection conn;
private void button1_Click(object sender, EventArgs e)
{
if (textBox1.Text == "")
{
MessageBox.Show("请输入正确的数据库名");
}
else
{
try
{
string constr = "server=127.0.0.1;database=" + textBox1.Text.Trim() + ";uid=sa;pwd=56119537";
SqlConnection conn = new SqlConnection(constr);
conn.Open();
if (conn.State == ConnectionState.Open)
{
MessageBox.Show("数据库连接成功");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
} private void button2_Click(object sender, EventArgs e)
{
try
{
conn.Close();
if (conn.State == ConnectionState.Closed)
{
MessageBox.Show("数据库断开成功");
}
conn.Open();
if (conn.State == ConnectionState.Open)
{
MessageBox.Show("数据库连接成功");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message );
}
}
}
}
为什么书上的代码和我基本差不多 为什么我就错了?
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
SqlConnection conn;
private void button1_Click(object sender, EventArgs e)
{
if (textBox1.Text == "")
{
MessageBox.Show("请输入正确的数据库名");
}
else
{
try
{
string constr = "server=127.0.0.1;database=" + textBox1.Text.Trim() + ";uid=sa;pwd=56119537";
SqlConnection conn = new SqlConnection(constr);
conn.Open();
if (conn.State == ConnectionState.Open)
{
MessageBox.Show("数据库连接成功");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
} private void button2_Click(object sender, EventArgs e)
{
try
{
conn.Close();
if (conn.State == ConnectionState.Closed)
{
MessageBox.Show("数据库断开成功");
}
conn.Open();
if (conn.State == ConnectionState.Open)
{
MessageBox.Show("数据库连接成功");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message );
}
}
}
}
为什么书上的代码和我基本差不多 为什么我就错了?
namespace 第15章_数据访问技术 //命名空间用中文不合适??
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
SqlConnection conn; //这里你既然作为全局变量,下面你又声明了一个完全相同的局部变量,有问题??
private void button1_Click(object sender, EventArgs e)
{
if (textBox1.Text == "")
{
MessageBox.Show("请输入正确的数据库名");
}
else
{
try
{
string constr = "server=127.0.0.1;database=" + textBox1.Text.Trim() + ";uid=sa;pwd=56119537";
SqlConnection conn = new SqlConnection(constr); //你的一个局部变量
conn.Open();
if (conn.State == ConnectionState.Open)
{
MessageBox.Show("数据库连接成功");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
} private void button2_Click(object sender, EventArgs e)
{
try
{
conn.Close();
if (conn.State == ConnectionState.Closed)
{
MessageBox.Show("数据库断开成功");
} conn.Open();
if (conn.State == ConnectionState.Open)
{
MessageBox.Show("数据库连接成功");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message );
}
}
}
}
namespace 第15章_数据访问技术 //命名空间用中文不合适??
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
SqlConnection conn; //这里你既然作为全局变量,下面你又声明了一个完全相同的局部变量,有问题??
private void button1_Click(object sender, EventArgs e)
{
if (textBox1.Text == "")
{
MessageBox.Show("请输入正确的数据库名");
}
else
{
try
{
string constr = "server=127.0.0.1;database=" + textBox1.Text.Trim() + ";uid=sa;pwd=56119537";
SqlConnectionconn = new SqlConnection(constr); //这里直接使用全局SqlConnection对象即可,无需再声明conn.Open();
if (conn.State == ConnectionState.Open)
{
MessageBox.Show("数据库连接成功");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
} private void button2_Click(object sender, EventArgs e)
{
try
{
conn.Close();
if (conn.State == ConnectionState.Closed)
{
MessageBox.Show("数据库断开成功");
} conn.Open();
if (conn.State == ConnectionState.Open)
{
MessageBox.Show("数据库连接成功");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message );
}
}
}
}
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
SqlConnection conn; //这里你既然作为全局变量,下面你又声明了一个完全相同的局部变量,有问题??
private void button1_Click(object sender, EventArgs e)
{
if (textBox1.Text == "")
{
MessageBox.Show("请输入正确的数据库名");
}
else
{
try
{
string constr = "server=127.0.0.1;database=" + textBox1.Text.Trim() + ";uid=sa;pwd=56119537";
conn = new SqlConnection(constr); //这里直接使用全局SqlConnection对象即可,无需再声明
conn.Open();
if (conn.State == ConnectionState.Open)
{
MessageBox.Show("数据库连接成功");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
} private void button2_Click(object sender, EventArgs e)
{
try
{
conn.Close();
if (conn.State == ConnectionState.Closed)
{
MessageBox.Show("数据库断开成功");
} conn.Open();
if (conn.State == ConnectionState.Open)
{
MessageBox.Show("数据库连接成功");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message );
}
}
}
}
namespace 第15章_数据访问技术
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
SqlConnection conn; //类变量 SqlConnection conn;
private void button1_Click(object sender, EventArgs e)
{
if (textBox1.Text == "")
{
MessageBox.Show("请输入正确的数据库名");
}
else
{
try
{
string constr = "server=127.0.0.1;database=" + textBox1.Text.Trim() + ";uid=sa;pwd=56119537";
SqlConnection conn = new SqlConnection(constr); //局部变量,与类变量重名
conn.Open();
if (conn.State == ConnectionState.Open)
{
MessageBox.Show("数据库连接成功");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
}
} private void button2_Click(object sender, EventArgs e)
{
try
{
conn.Close();
if (conn.State == ConnectionState.Closed)
{
MessageBox.Show("数据库断开成功");
}
conn.Open();
if (conn.State == ConnectionState.Open)
{
MessageBox.Show("数据库连接成功");
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message );
}
}
}
}