C Sharp :: Opening And Importing Multiple Files Into DataGridView / Database

I'm trying to add a function now that lets the user open 1 or more files and import them to the database and dataGridView. Now the way it is now (should) work. But when it has finished with FILE1, it won't add FILE2 as it then gives me an error that the Column Date Already exists.

My code is below

private void btnOpenLog_Click(object sender, EventArgs e)   {
            OpenFileDialog openFileDialog1 = new OpenFileDialog();
            openFileDialog1.Filter = "Log Files (*.log)|*.log";
            openFileDialog1.Multiselect = true;

[Code] .....