How to check if table is empty in VB.net [duplicate] - sql

Question

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Closed 12 years ago.
Possible Duplicate:
Checking for an SQL result in VB.NET
I have login form which is redirect user for their levels but before to that if there is no any user on the data table I would like to redirect to create admin form. I have all the forms but I didn't manage to redirect them because I don't know how to create statement. Could you please help me about solution.
Dim con As SqlCeConnection
Dim command As SqlCeCommand
con = New SqlCeConnection("Persist Security Info=False;Data Source=.\database.sdf;Password=********;File Mode=shared read")
con.Open()
command = New SqlCeCommand("select * from users where Name=? and Password=?", con)
Dim param1, param2 As SqlCeParameter
param1 = New SqlCeParameter("Name", uname.Text)
param2 = New SqlCeParameter("Password", pwd.Text)
command.Parameters.Add(param1)
command.Parameters.Add(param2)
Dim reader As SqlCeDataReader = command.ExecuteReader
If (reader.Read = True) Then
role = reader.GetString(1)
Else
MsgBox("Invalid Login")
End If
I have this code is working. What to write for
Private Sub frmlogin_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
End Sub

Answer 1

I would recommend trying the DataReader's HasRows property to determine if one or more rows was returned to the DataReader object.
if (reader.HasRows)
{
reader.Read();
role = reader.GetString(1)
}
else
{
// invalid login
}

Answer 2

Not sure I completely understand your question, but if the table is empty then reader.Read() would evaluate to False.
I think what you want is a SQL Statement checking the Count of the users table.
Something like
command = New SqlCeCommand("SELECT COUNT(Name) as NameCount FROM Users", con)
Then you would evaluate the count by doing something like
Dim reader as SqlCeDataReader = command.ExecuteReader()
While(reader.Read())
if reader("NameCount") = 0 then
'Redirect to Admin Form
else
'Run all your current logic here to find the user from the DB
end if
End While