how to check if user is in database already ?

Question

I have a form which requires new user to register. If they are already in the database, then they will be re-direct to the login page. If not, they can proceed with the user registration.

However, I am not sure what is wrong with my code cos even if the username is not found, it still direct them to the login page.

protected void Submit_Button_Click(object sender, EventArgs e)
{
using (Team6_PhoneOnlineShopEntities2 cntx = new Team6_PhoneOnlineShopEntities2())
{
//try
{
// var checkuser = from u in cntx.Users where u.userName == txtUserName.Text select u;
// var checkuser = from u in cntx.Users where txtUserName.Text == u.userName select u;
var checkuser = cntx.Users.FirstOrDefault(u => txtUserName.Text == u.userName);
//int a = Convert.ToInt32(txtUserId.Text);
// var User = cntx.Users.FirstOrDefault(m => m.userID == a);
// customer.userName = txtUserName.Text;
// String checkUser = "select Count(*) from User where userName = '" + customer.userName + "'";
if (checkuser == null)
{
User customer = new User();
customer.userName = txtUserName.Text;
customer.lastName = txtLastName.Text;
customer.userPassword = txtUserPassword.Text;
customer.userPassword = txtConfirmedPassword.Text;
customer.moblieNumber = txtMobileNo.Text;
customer.userAddress = txtAddress.Text;
customer.userEmail = txtEmail.Text;
customer.roleID = 1;
customer.paymentMethod = DropDownList1.SelectedValue;
cntx.Users.Add(customer);
cntx.SaveChanges();
lblMessageSuccess.Text = "successful registration";
}
else
{
lblMessageUser.Text = "You have registered before. Pls proceed to login";
Response.Redirect("/Login.aspx");
}
}
// Response.Redirect("SuperPhoneOnLineShop_Team6/ShoppingPage");// enter the right url here
}
}
}
}

I hope someone can point out what is the way to do my code so that it will turn out the way I want. Many thanks.

Tangara G · Answer

Re Manas I am a beginner and that is where I am stuck .. How do I validate if the user is already in the database before I use the LINQ ? And without using javascript. How do you write that method ? assuming I have a web service and DAO layer ? If you can give me a quick illustration I will be most appreciative.

Imran Bashir · Answer

use this store procedure CREATE procsp_wuser_register @user_name varchar (50) @ password varchar (50) @first_name varchar (50) @last_name varchar (50) @address varchar (100) @contact varchar (50) as begin declare @ count int declare @ReturnCode int Select @ count = COUNT (user_name) from user_reg where user_name=@user_name if@ count >0 begin set @ReturnCode=-1 end else begin set @ReturnCode=1 insert into user_reg values (@user_name@ password @first_name@last_name@address@contact) End select @ReturnCode as ReturnValue End in project u call this like protected void btnSubmit_Click(object sender EventArgs e) { if (Page.IsValid) { using (db.con) { db.com = new SqlCommand(sp_user_register db.con); db.com.CommandType = CommandType.StoredProcedure; //string khan = DateTime.Now.ToString(); db.com.Parameters.AddWithValue(@user_nametxtUserName.Text.Trim()); db.com.Parameters.AddWithValue(@passwordtxtPassword.Text.Trim()); db.com.Parameters.AddWithValue(@first_name txtFirstName.Text.Trim()); db.com.Parameters.AddWithValue(@last_nametxtLastName.Text.Trim()); db.com.Parameters.AddWithValue(@addresstxtAddress.Text.Trim()); db.com.Parameters.AddWithValue(@contacttxtPhone.Text.Trim()); try { db.con.Open(); int ReturnCode = (int)db.com.ExecuteScalar(); if (ReturnCode == -1) { lblResult.Text = user name is already in use; } else { ScriptManager.RegisterClientScriptBlock(this this.GetType() alertMessage alert('Record Inserted Successfully') true); Response.AddHeader(REFRESH 2;URL=regSalesman.aspx); } } catch (Exception ex) { lblResult.Text = ex.Message; } } } else lblResult.Text = some Fields are missing; } }

Manas Mohapatra · Answer

You must have to validate the textbox value before you use LINQ.

Tangara G · Answer

Hi Manas Can I know why you are comparing with txtUserName.Text when the user has not even enter the text into the Textbox ? int noOfUsers = cntx.Users.Count(u => u.userName == txtUserName.Text);

ali tuncer · Answer

Hi Karen Best way is to put a breakpoint and debug your code. If username does not exist checkuser has to be null so it shouldn't go to else part...you need to check the value of checkuser variable..

Tangara G · Answer

Hi Ali Form based there is a built in validator control to check plus regular express so the empty part is already taken care of. Where as your linq statement it is the same as what I have been using. var checkuser = cntx.Users.Where(u => u.userName == txtUserName.Text).FirstOrDefault(); Seems like here has nobody who knows the answer..... Actually I think I may have to write some validation method at in separate class and call it. If the result is negative..meaning the user is not exist then I will let the user continue with the registration form....

Manas Mohapatra · Answer

Try with below code: int noOfUsers = cntx.Users.Count(u => u.userName == txtUserName.Text); if (noOfUsers == 0) { // Add User to DB }

ali tuncer · Answer

what if txtUserName.Text is empty? since you don't validate before you save you might be saving empty values(blanks) to database..check the records in your database.. try this code to check is username exists : var checkuser = cntx.Users.Where(u => u.userName == txtUserName.Text).FirstOrDefault ();

Tangara G · Answer

Bikesh Your answer is incorrect cos it is not what I was asking for. I need to check if the user is in the database and then if it is I will need to direct the user to the login page otherwise the user will continue to fill up all the textbox form and able to submit the details to the database. Assumption I already create the connectively layer ....so i just need that server validation portion....

Bikesh Srivastava · Answer

Hi karen. use code like this to exist user. protected void btn_check_Click( object senderEventArgse) { SqlConnectioncon= new SqlConnection(connStr); con.Open(); str= selectcount(*)fromemployeewhereename=' +txtUserName.Text+ ' ; com= new SqlCommand(strcon); int count=Convert.ToInt32(com.ExecuteScalar()); if (count>0) { lblMessage.Text= usernameexist ; } else { lblMessage.Text= usernamedoesnotexist ; } } If its resolve your query mark as answer.