VB.NET DataTable rows - sql-server

Question

I'm trying to make a login form.
I've created a database on my server and created the rows username and password.
I then created a root user with root as password.
but I have a problem with the check if the username and password are correct,
I don't know how to give him the 2 rows.
Dim conn = New SqlConnection("Data Source=SRV-SQL;Initial Catalog=prova;User ID=user;Password=user")
Dim sda = New SqlDataAdapter("select count(*) from tblLogin where username ='" + txtUsername.Text + "' and password='" + txtUserPwd.Text + "'", conn)
Dim dt = New DataTable()
sda.Fill(dt)
If (dt.Rows().ToString() = "1") Then
MsgBox("Logged-in successfully")
Else
MessageBox.Show("The username or the password is wrong!", "Warning!", MessageBoxButtons.OK, MessageBoxIcon.Error)
End If
Table:

Answer 1

Comments and explanations in-line.
Private Sub VerifyLogin()
'For the Return Value of the command
Dim RetVal As Integer
' A Using...End Using will ensure that you connectionis closed and disposed event
'it there is an error.
Using conn = New SqlConnection("Data Source=SRV-SQL;Initial Catalog=prova;User ID=user;Password=user")
'You don't need a DataAdapter, just a command
'USE PARAMETERS. Yes, I am yelling :-) Even if you are the only user
'it will save you headaches with syntax.
Using cmd = New SqlCommand("select count(*) from tblLogin where username = #UserName and password= #Password;", conn)
cmd.Parameters.Add("#UserName", SqlDbType.VarChar).Value = txtUsername.Text
cmd.Parameters.Add("#Password", SqlDbType.VarChar).Value = txtUserPwd.Text
'You are only returning one row
'ExecuteScalar returns the value in the first column of the
'first row of the the data
conn.Open()
RetVal = CInt(cmd.ExecuteScalar)
End Using
End Using
'No need to convert to a string just compare the Integer
If RetVal = 1 Then
MsgBox("Logged-in successfully")
Else
MessageBox.Show("The username or the password is wrong!", "Warning!", MessageBoxButtons.OK, MessageBoxIcon.Error)
End If
End Sub

Answer 2

Private Function CalculateHash(password As String, salt As String) As String
'TODO:
' Suggest pulling the BCrypt from the NuGet gallery for this:
' https://www.nuget.org/packages/BCrypt-Official/
' Just remember that bcyrpt lib encodes salt as part of the password hash, so the function signatures and db table will be different.
End Function
Public Function CheckCredentials(UserName As String, Password As String) As Boolean
Using conn As New SqlConnection("Data Source=SRV-SQL;Initial Catalog=prova;User ID=user;Password=user"), _
' Need to add a "Salt" column to your table, create a new random salt for each user when you create the user
cmd As New SqlCommand("SELECT Salt, PwdHash FROM tblLogin WHERE username = #Username", conn)
'Parameterized queries or NOTHING. String concatention is NOT OKAY here
cmd.Parameters.Add("#UserName", SqlDbType.NVarChar, 50).Value = UserName
conn.Open()
Using rdr As SqlDataReader = cmd.ExecuteReader()
If Not rdr.Read() Then Return False
Dim Salt As String = rdr("Salt")
Dim PwdHash As String = rdr("PwdHash")
'Compare HASHES, not Passwords
Return PwdHash = CalculateHash(Password, Salt As String)
End Using
End Using
End Function
If CheckCredentials(txtUsername.Text, txtUserPwd.Text) Then
MsgBox("Logged-in successfully")
Else
MessageBox.Show("The username or the password is wrong!", "Warning!", MessageBoxButtons.OK, MessageBoxIcon.Error)
End If

Answer 3

Use DataReader instead, use this code and just call CheckLogin in login button or somthing else.
Sub CheckLogin()
Dim conn = New SqlConnection("Data Source=SRV-SQL;Initial Catalog=prova;User ID=user;Password=user")
conn.Open()
Try
Dim query As String = "select count(*) from tblLogin where username = #username and password= #password "
Dim cmd = New SqlCommand(query, conn)
cmd.Parameters.AddWithValue("#username", txtUsername.Text)
cmd.Parameters.AddWithValue("#password", txtUserPwd.Text)
Dim DR As SqlDataReader = cmd.ExecuteReader()
If DR.HasRows Then
MsgBox("Logged-in successfully")
Else
MessageBox.Show("The username or the password is wrong!", "Warning!", MessageBoxButtons.OK, MessageBoxIcon.Error)
End If
Catch ex As Exception
MsgBox(ex.Message)
End Try
conn.Close()
End Sub