Why does my code only read first row in database? - vb.net

Question

Dim con As New SqlConnection
con.ConnectionString = "Data Source=(local);Integrated Security=True"
Dim cmd As New SqlCommand("SELECT * FROM login where Admin = #Admin AND Password = #Password ", con)
'Set up parameters for the sqlcommand
cmd.Parameters.AddWithValue("#Admin", comb.Text)
cmd.Parameters.AddWithValue("#Password", Txtpass.Text)
'If the username or password is empty then throw an error
If comb.Text = String.Empty Then
MessageBox.Show("Please choose the username.", Me.Text, MessageBoxButtons.OK, MessageBoxIcon.Error)
ElseIf Txtpass.Text = String.Empty Then
MessageBox.Show("Please enter the password.", Me.Text, MessageBoxButtons.OK, MessageBoxIcon.Error)
Else
Try
'Open the connection and declare an sqlreader
con.Open()
Dim reader As SqlDataReader = cmd.ExecuteReader
'If our reader has one or more rows then read those rows and compare the text
If reader.HasRows = True Then
reader.Read()
Dim ReadUserName As String
Dim ReadUserID As String
ReadUserID = reader(3) 'This is the first field returned, most likely UserID
ReadUserName = reader(1) 'This is the second field returned
'If the username and password match then it's a success
If comb.Text = reader("Admin").ToString And Txtpass.Text = reader.Item("Password").ToString Then
MessageBox.Show("Login successful" & ReadUserName)
Else
'If they don't match than throw an error
MessageBox.Show("Login Failed." & Environment.NewLine & _
"UserName and Password are casesensitive.", _
Me.Text, MessageBoxButtons.OK, MessageBoxIcon.Error)
End If
End If
Catch ex As Exception
MessageBox.Show(ex.ToString, Me.Text, MessageBoxButtons.OK, MessageBoxIcon.Error)
Finally
con.Close()
End Try
End If

Answer 1

You're telling your code to read one row:
If reader.HasRows = True Then
reader.Read()
If you want to read all rows from your SqlDataReader, you need to use a loop (here in C#):
while (reader.Read())
{
..... (read the individual values for the current row) ......
}
The .Read() call will return true, as long as a row has been read from the SqlDataReader - now fetch the data from the row, store it or process it - whatever you need to do - and then your next call to reader.Read() checks if another row can be read. If so: repeat your processing.
If reader.Read() return false, then all rows have been read and you're done.

Answer 2

If command runs the code only once and read one row. So use while loop to read all the line
If reader.HasRows = True Then
While reader.Read()
Dim ReadUserName As String
Dim ReadUserID As String
ReadUserID = reader(3) 'This is the first field returned, most likely UserID
ReadUserName = reader(1) 'This is the second field returned
'If the username and password match then it's a success
If comb.Text = reader("Admin").ToString And Txtpass.Text = reader.Item("Password").ToString Then
MessageBox.Show("Login successful" & ReadUserName)
Else
'If they don't match than throw an error
MessageBox.Show("Login Failed." & Environment.NewLine & _
"UserName and Password are casesensitive.", _
Me.Text, MessageBoxButtons.OK, MessageBoxIcon.Error)
End If
End While ' I don't know much of vb.net'
End If