Question

ExecuteScalar: CommandText 属性尚未初始化

代码如下：
namespace GradeManagerSystem{ public partial class UpdatePassword : Form { public UpdatePassword() { InitializeComponent(); }
private void button1_Click(object sender, EventArgs e) { if (textBox1.Text == "") { MessageBox.Show("用户名不能为空！"); textBox1.Select(); } else if (textBox2.Text == "") { MessageBox.Show("旧密码不能为空！"); textBox2.Select(); } else if (textBox3.Text == "") { MessageBox.Show("新密码不能为空！"); textBox3.Select(); } else if (textBox2.Text == textBox3.Text) { MessageBox.Show("两次输入密码一致，请重新输入！"); } else { string sql = "select count(*) from useraccount where username='" + textBox1.Text + "' and password='" + textBox2.Text + "'"; string sql1 = "update useraccount set password='" + textBox3.Text + "' where username='" + textBox1.Text + "'"; string connstr = System.Configuration.ConfigurationSettings.AppSettings["connstr"]; SqlConnection conn = new SqlConnection(connstr); SqlCommand cmd = new SqlCommand(); cmd.Connection = conn; cmd.Connection.Open(); int n = Convert.ToInt32(cmd.ExecuteScalar()); cmd.Connection.Close(); if (n <= 0) { MessageBox.Show("你输入的用户名或旧密码有误，请重新输入！"); this.textBox1.Text = ""; textBox1.Select(); } else { cmd.Connection.Open(); cmd.ExecuteNonQuery(); cmd.Connection.Close(); MessageBox.Show("修改用户密码成功！"); } } } }}

Answer 1

string sql = "select count(*) from useraccount where username='" + textBox1.Text + "' and password='" + textBox2.Text + "'";
string sql1 = "update useraccount set password='" + textBox3.Text + "' where username='" + textBox1.Text + "'";
string connstr = System.Configuration.ConfigurationSettings.AppSettings["connstr"];
SqlConnection conn = new SqlConnection(connstr);
SqlCommand cmd = new SqlCommand();
cmd.Connection = conn;
cmd.Connection.Open();
cmd.CommandText=sql;///////////////////////////注意添加查询内容
int n = Convert.ToInt32(cmd.ExecuteScalar());
cmd.Connection.Close();
if (n <= 0)
{
MessageBox.Show("你输入的用户名或旧密码有误，请重新输入！");
this.textBox1.Text = "";
textBox1.Select();
}
else {
cmd.CommandText=sql1;///////////////////注意添加修改内容
cmd.Connection.Open();
cmd.ExecuteNonQuery();
cmd.Connection.Close();
MessageBox.Show("修改用户密码成功！");
} } } }

追问

什么意思？

追答

cmd中都没有执行的SQL语句 没看到添加进去的内容嘛