Error database is locked sqlite vb.net - database

Question

hi I'm trying to insert a row to my database but I still get this error message (see below):
I used the methode using to be sure that the connection will be closed.
below the script for the insert button :
Private Sub MTB_Insert_Click(sender As Object, e As EventArgs) Handles MTB_Insert.Click
cmd = New SQLite.SQLiteCommand
Using con As New SQLite.SQLiteConnection(constr)
Try
'con.ConnectionString = constr
con.Open()
cmd.Connection = con
cmd.CommandText = "Insert Into Material_Type (Material_Type,Material_Type_Description) values(#Type,#Description)"
cmd.Parameters.AddWithValue("#Type", MTTB_Material_Type.Text)
cmd.Parameters.AddWithValue("#Description", MTTB_Material_Description.Text)
cmd.ExecuteNonQuery()
MessageBox.Show("Successful Added Data")
'Calling function load data
loadDatadg1()
'con.Dispose()
'con.Close()
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
End Using
End Sub
other parts of my code :
Public Class F_Update
Dim con As SQLite.SQLiteConnection
Dim cmd As SQLite.SQLiteCommand
Dim da As SQLite.SQLiteDataAdapter
Dim constr As String = "Data source =Database1.db"
Public Sub loadDatadg1()
Using con As New SQLite.SQLiteConnection(constr)
'con = New SQLite.SQLiteConnection(constr)
con.Open()
Dim str As String = "select * from Material_type"
da = New SQLite.SQLiteDataAdapter(str, con)
Dim ds As New DataSet
da.Fill(ds, "Tb.Material_Type")
dg1.DataSource = ds.Tables("Tb.Material_Type")
'da.Dispose()
'con.Close()
End Using
End Sub
Private Sub F_Update_Load(sender As Object, e As EventArgs) Handles MyBase.Load
Using con As New SQLite.SQLiteConnection(constr)
' con = New SQLite.SQLiteConnection(constr)
con.Open()
'MsgBox("OK")
'Calling the function Load form
loadDatadg1()
End Using
End Sub
another part :
Private Sub B_login_Click(sender As Object, e As EventArgs) Handles B_login.Click
Dim connectionString As String = "Data source =Database1.db"
Dim mSQL As String = "select User_Name,User_Password from User where (User_ID = 1 and User_Name = '" & T_User_Name.Text & "' and User_Password = '" & T_User_Password.Text & "')"
Dim dt As DataTable = Nothing
Dim ds As DataSet
Dim rd As SQLiteDataReader
Using con As New SQLiteConnection(connectionString)
Try
con.Open()
Dim cmd As New SQLiteCommand(mSQL, con)
cmd.ExecuteNonQuery()
rd = cmd.ExecuteReader
Catch ex As Exception
MessageBox.Show(ex.Message)
End Try
If rd.HasRows Then
F_Update.Show()
Me.Close()
Else
MessageBox.Show("Invalid User Name or Password")
End If
'con.Close()
End Using
End Sub
End Class
can some one help me please ? Thanks in advance