How Can I Validate If One Email Address Exists Or Not In A Given Database

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Hi everyone

I am working on a project and I am having trouble checking if one email address exists in my user table and I want to validate it before submitting the values. I have attached my code below. Thanks in advance.

C#

SqlConnection lytCom = new SqlConnection(ConfigurationManager.ConnectionStrings["constrlyt"].ConnectionString);
lytCom.open();
SqlCommand check_User_Name = new SqlCommand("SELECT COUNT(email) FROM [company] WHERE ([email] = @email)", lytCom);
            check_User_Name.Parameters.AddWithValue("@email", txtEmail.Text);
            int UserExist = (int)check_User_Name.ExecuteScalar();
            lblStatus.Text = UserExist.ToString();
            if (UserExist > 0)
                    {
                        lblStatus.Text = "Email Already Exists";
                        btnReg.Enabled = false;
                        lytCom.Close();
                    }
            else
                    {
                

                       btnReg.Enabled = true;
                        SqlCommand sqlcmd = new SqlCommand("insert into company (company_name,email,admin_password,date_joined) values ('" + txtCompName.Text + "','" + txtEmail.Text + "','" + lblEncryptedText.Text + "','" + System.DateTime.Now.ToString() + "')", lytCom);
                        sqlcmd.CommandType = CommandType.Text;
                        sqlcmd.ExecuteNonQuery();
                        lytCom.Close();
                        Response.Redirect("LogIn.aspx");
                        ClientScript.RegisterStartupScript(GetType(), "alert", "alert('Welcome');", true);

                }

Posted 23-Dec-15 2:27am

Faysel Kedir

Updated 23-Dec-15 8:10am

Mike Meinz

v3

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Mike Meinz 23-Dec-15 8:41am

You don't say what kind of problem you are having so it is difficult to know how to help you.

I did spot two things that may or may not make a difference.
I would change these two lines to this:

SqlCommand check_User_Name = new SqlCommand("SELECT COUNT(*) FROM [company] WHERE ([email] = @email)", lytCom);
check_User_Name.Parameters.AddWithValue("email", txtEmail.Text.Trim().ToLower());

Faysel Kedir 23-Dec-15 8:52am

Dear i want to validate whether given email address exists or not in the database.

Mike Meinz 23-Dec-15 8:57am

Yes, you said that in your question. But you said you had a problem. What is the problem? Are you getting an error message? If so, what is it?

Faysel Kedir 23-Dec-15 9:37am

currently my code is leting the user to insert same email address again and again

Mike Meinz 23-Dec-15 9:59am

1. Did you make the changes that I suggested in my first comment?
SqlCommand check_User_Name = new SqlCommand("SELECT COUNT(*) FROM [company] WHERE ([email] = @email)", lytCom);
check_User_Name.Parameters.AddWithValue("email", txtEmail.Text.Trim().ToLower());
2. Is this problem caused by the fact that one or more of the letters in an email address in the database are of a different case then the letters entered by the user? See #5 below.
3. Make sure there are no spaces before or after the email address in the database.
4. The SQL INSERT statement should use SQLParameters like you do for the SQL SELECT statement. All ".Text" properties on the right side of an assignment statement should be coded as ".Text.Trim()" so that extraneous spaces are removed. Also, using SQLParameters prevents SQL Injection Attacks.
Like this:
SqlCommand sqlcmd = new SqlCommand("INSERT INTO company (company_name,email,admin_password,date_joined) VALUES(@CompName,@Email,@Encrypted,@TimeStamp);", lytCom);
sqlcmd.Parameters.AddWithValue("CompName",txtCompName.Text.Trim());
sqlcmd.Parameters.AddWithValue("Email",txtEmail.Text.Trim().ToLower());
sqlcmd.Parameters.AddWithValue("Encrypted",lblEncryptedText.Text.Trim());
sqlcmd.Parameters.AddWithValue("TimeStamp",System.DateTime.Now.ToString());
5. Run this SQL UPDATE statement in SQL Management Studio to ensure there are no extraneous spaces and all email addresses are in all lower-case.
UPDATE company SET email=LOWER(LTRIM(RTRIM(email)))

Faysel Kedir 25-Dec-15 13:14pm

thanks for the help bro,but i just tried the steps you suggested and it ain't working !

Mike Meinz 25-Dec-15 13:40pm

At this point, I think you should use the Visual Studio debugger and step through the code to find your problem. I still think it may be extraneous spaces or letter case mismatch but I can't see your data so I can't be more help.

Mike Meinz 25-Dec-15 13:42pm

Maybe you could modify the question to show the current state of your source code. That way, I can be sure you made all the changes that I suggested.

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OriginalGriff · Accepted Answer · 2015-12-23T02:58:00

Solution 1

Use ExecuteScalar to run something like this:

C#

using (SqlCommand cmd = new SqlCommand("SELECT COUNT(*) FROM MyTable WHERE EmailColumn=@EM", con)
   {
   cmd.Parameters.AddWithValue("@EM", emailTheUserTyped);
   int count = (int) cmd.ExecuteScalar();
   if (count != 0)
      {
      // It's in there...
      }
   }

Posted 23-Dec-15 2:58am

OriginalGriff

Comments

Faysel Kedir 26-Dec-15 2:49am

Appreciate all the support and help from all of you, it meant a lot!