连接属性未初始化 [英] connection property not initialized in

问题描述

SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["abc"].ConnectionString);
SqlCommand cmd;


cmd = new SqlCommand("insert into student (name,email,mobile,userid,pass) values('"+textBox1.Text+"','"+textBox2.Text+"','"+textBox3.Text+"','"+textBox4.Text+"','"+textBox5.Text+"')", con);
cmd = new SqlCommand("insert into course (stid) select top (1) stid from student order by stid desc", con);
cmd = new SqlCommand("insert into course (coursename)values ('" + comboBox1.Text + "') select top (1) stid from course order by stid desc");
//cmd.CommandType = CommandType.StoredProcedure;

//cmd.Parameters.AddWithValue("@name", textBox1.Text);
//cmd.Parameters.AddWithValue("@email", textBox2.Text);
//cmd.Parameters.AddWithValue("@mobile", textBox3.Text);
//cmd.Parameters.AddWithValue("@userid", textBox4.Text);
//cmd.Parameters.AddWithValue("@pass", textBox5.Text);
//cmd.Parameters.AddWithValue("@username", cmd);
con.Open();
cmd.ExecuteNonQuery();
con.Close();

推荐答案

cmd = new SqlCommand("insert into course (coursename)values ('" + comboBox1.Text + "') select top (1) stid from course order by stid desc");

相同的对象在上面的代码中被使用3次。第三次连接属性未传递给命令对象。

same object intilized 3 times in above code.in third time connection property not passed to command object.

cmd = new SqlCommand("insert into course (coursename)values ('" + comboBox1.Text + "') select top (1) stid from course order by stid desc");

用以下代码替换此代码。

replace this code with below.

cmd = new SqlCommand("insert into course (coursename)values ('" + comboBox1.Text + "') select top (1) stid from course order by stid desc",con);

您已将值设置为cmd对象三次。因此，您的cmd onject将保留最后提供的最新值。在你的第三个初始化语句中

You have set the value to cmd object three times. So your cmd onject will hold the latest value which has been provided in the very last. In your third initialization statement

cmd = new SqlCommand("insert into course (coursename)values ('" + comboBox1.Text + "') select top (1) stid from course order by stid desc");

你没有提供con对象。即没有传递给命令对象的连接对象，这就是为什么cmd对象的连接属性未初始化的原因。



你的陈述应该是

you have not provided the con object. ie there is no connection object passed to command object thats why your connection property of cmd object not initialized.

your statement should be

cmd = new SqlCommand("insert into course (coursename)values ('" + comboBox1.Text + "') select top (1) stid from course order by stid desc",con);

原因：未设置连接对象使用SqlCommand对象。因此，当尝试执行inittenonquery（）时，它会搜索未设置的连接对象并抛出异常。



在您的代码中3次初始化SqlCommand对象和第三次（最后）你没有设置连接对象。请使用以下代码：

Reason: Connection object is not set with SqlCommand object. So when trying to executenonquery() it searches connection object which is not set and throwing you exception.

In your code 3 times you are initializing SqlCommand object and third time(last) you didn't set connection object. Please use below code:

cmd = new SqlCommand("insert into course (coursename)values ('" + comboBox1.Text + "') select top (1) stid from course order by stid desc", con);

注意：你正在初始化SqlCommand对象3次，你是否正在尝试更多的东西来实现。因为总是最后的初始化语句会起作用。



请使用参数化查询以避免SQL注入。

Note: You are initializing SqlCommand Object 3-times, are you trying anything more to achieve. Because always last initialization statement will work.

Please use parameterized query in order to avoid SQL injection.

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