我开始学习ASP.NET。我创建了一个注册系统，当我尝试检查用户名或电子邮件是否已存在于数据库中时，即使用户已经拥有该用户名或电子邮件，也不会对其进行检查并创建用户。
try
{
conn.Open();
bool exists = false;
string checkuser = "SELECT count(*) FROM accounts WHERE username='" + username.Text + "'";
SqlCommand cmd2 = new SqlCommand(checkuser, conn);
cmd2.Parameters.AddWithValue("username", username.Text);
exists = (int)cmd2.ExecuteScalar() > 0;
if (exists)
{
Response.Write("User already exists");
}
string command = "INSERT INTO accounts (username, email, password) VALUES (@username, @email, @password)";
SqlCommand cmd = new SqlCommand(command, conn);
cmd.Parameters.AddWithValue("@username", username.Text);
cmd.Parameters.AddWithValue("@email", email.Text);
cmd.Parameters.AddWithValue("@password", password.Text);
cmd.ExecuteNonQuery();
}
catch(Exception)
{
label_msg.Visible = true;
label_msg.Text = "Something went wrong....";
throw;
}
finally
{
Response.Redirect("/layout.aspx");
conn.Close();
}
谢谢 ！
检查用户是否已经存在
int exists = 0;
string checkuser = "SELECT count(*) FROM accounts WHERE username='" +username.Text + "'";
SqlCommand cmd2 = new SqlCommand(checkuser, conn);
cmd2.Parameters.AddWithValue("username", username.Text);
exists = (int)cmd2.ExecuteScalar();
if (exists>0)
{
Response.Write("User already exists");
}
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