'System.InvalidOperationException' occurred in System.Data.dll - vb.net

Question

I'm doing a simple login page for Visual Basic connected to an access database and I keep receiving this error when I run the project.
I would greatly appreciate it if anyone could help me resolve this.
Imports System.Data.OleDb
Public Class frmLogin
Dim objConnection As New OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=Login.accdb")
Dim objDA As New OleDb.OleDbDataAdapter("SELECT * FROM User", objConnection)
Dim objCB As New OleDb.OleDbCommandBuilder(objDA)
Dim objDS As New DataSet()
Public Username, Password As String
Dim UserFound As Boolean
Private Sub frmLogin_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Retrieve()
End Sub
Private Sub btnLogin_Click(sender As Object, e As EventArgs) Handles btnLogin.Click
Username = txtUser.Text
Password = txtPassword.Text
For i As Integer = 1 To (objDS.Tables("User").Rows.Count)
If CStr(objDS.Tables("User").Rows(i - 1).Item("Username")) =
Username And
CStr(objDS.Tables("User").Rows(i - 1).Item("Password")) = Password Then
UserFound = True
Me.Hide()
MessageBox.Show("Welcome to the System!")
frmStudents.Show()
Exit For
End If
txtUser.Text = String.Empty
txtPassword.Text = String.Empty
Next
If UserFound = False Then
MessageBox.Show("Access Denied")
End If
End Sub
Private Sub Retrieve()
objDS.Clear()
objDA.FillSchema(objDS, SchemaType.Source, "User")
objDA.Fill(objDS, "User")
End Sub
End Class
The error occurs in this line:
objDA.FillSchema(objDS, SchemaType.Source, "User") "User" is
underlined in the error
This is further info on the error shown:
An unhandled exception of type 'System.InvalidCastException' occurred
in Microsoft.VisualBasic.dll Additional information: Conversion from
string "User" to type 'Integer' is not valid

Answer 1

Instead of hauling down the entire users table just to verify a user get the count of records that match. Of course, in a real application, you would never store password as plain text.
Private Sub VerifyUser()
Dim objConnection As New OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0; Data Source=Login.accdb")
Dim cmd As New OleDbCommand("Select Count(*) From Users Where [Username] = #Username and [Passwor] = #Password;", objConnection)
cmd.Parameters.Add("#Username", OleDbType.VarChar).Value = txtUsername.Text
cmd.Parameters.Add("#Password", OleDbType.VarChar).Value = txtPassword.Test
objConnection.Open()
Dim count As Integer = CInt(cmd.ExecuteScalar())
Dim message As String = ""
If count > 0 Then
message = "Welcome"
Else
message = "Sorry"
End If
MessageBox.Show(message)
End Sub