An unhandled exception of type 'system.argumentexception' occurred in mscorlib.dll additional information: illegal characters in path.

doc.Load(selectedFile);

public partial class frmEditXML : Form
   {
       //get files from directory
       string[] path = Directory.GetFiles(@"C:\Users\decraiec\Documents\A_Automated", "*.XML");

       public frmEditXML()
       {
           InitializeComponent();
       }

       private void btnSelectFile_Click(object sender, EventArgs e)
       {
           openFileDialog1.Filter = "xml files|*.xml|All files|*.*";
           if (openFileDialog1.ShowDialog() == DialogResult.OK)
           {
               try
               {
                   richTextBox1.LoadFile(openFileDialog1.FileName, RichTextBoxStreamType.PlainText);
               }
               catch (Exception exc)
               {
                   MessageBox.Show("An error occured: " + System.Environment.NewLine + exc.ToString() + System.Environment.NewLine);
                   throw;
               }
           }
       }

       private void btnMakeNegative_Click(object sender, EventArgs e)
       {
           //Read selected file
           string selectedFile = richTextBox1.Text;
           XmlDocument doc = new XmlDocument();
           doc.Load(selectedFile); // --> error message
           //find the node to change the content
           //if node is not present, do nothing
           foreach (XmlNode xNode in doc)
           {
               if (xNode.ParentNode.Attributes["*.*"].Value != "")
               {
                   doc.SelectSingleNode("Identification").InnerText = "string";
                   doc.SelectSingleNode("SCI").InnerText = "string";
                   doc.SelectSingleNode("ReferenceType").InnerText = "string";
                   doc.SelectSingleNode("CCType").InnerText = "AA";
               }
               else { } //do nothing
           }

       }

       private void btnSavechanges_Click(object sender, EventArgs e)
       {
           if (saveFileDialog1.ShowDialog() == System.Windows.Forms.DialogResult.OK)
           {
               File.WriteAllText(saveFileDialog1.FileName, richTextBox1.Text);
           }
       }

       private void btnConvertToXML_Click(object sender, EventArgs e)
       {
           Form2 frm2 = new Form2();
           frm2.Show();

       }

       private void frmOpenRead_Load(object sender, EventArgs e)
       {
           Application.Exit();
       }


   }