Replace \\ with \ in FolderDialogBox.SelectedPath
private void label1_Click(object sender, EventArgs e)
    {
       folderBrowserDialog1.ShowNewFolderButton = false;

        if (folderBrowserDialog1.ShowDialog() == DialogResult.OK)
        {
            string p = @folderBrowserDialog1.SelectedPath; //=> Selected C:ACTNT
            //removing @ in front of folderBrowserDialog1 does not change the situation
            strPathName.Text = p; // => display c:ACNT
            con = "database = " + p; // => actual value "database = c:\ACNT"
            UpdateTableName();
        }
    }

string myvar = @"c:myfile.txt";

string path = @"C:\test";
path=path.Replace(@"\", @"");

@"c:test".