how to disable datagridview mouse click event for headers in c# -

I am trying to get value from the DataGrid view on mouse click event.

Works great if I do not click in the data grid view, I get an error saying this:

  The index was outside of the non-negative and Must be less than the size of the collection. The name of the parameter:   
 I use this code to locate the mouse click:  
  Private Zero Datagram View 1_CellMouseClick (Object Sender, Data Grid ViewMobileAvenEventErgusE) {if (DataGridView1.Rows [E.Rindex] .index! = -1) {Textbox 1 text = DataGrid viu1. ROS [E. ROExX]. Seals [0]. Value Toasting (); } Other {textBox1.Text = ""; }}   
 
 "DataGride View 1.RO [E. Randex] .index! = -1" does not work and I do not know why.   
 There will be no easy solution to disable the mouse click on the header! Thanks!  
 I also use it:  
  dataGridView1.SelectionMode = DataGridViewSelectionMode.FullRowSelect;   
 The entire column and cell content does not work to select. If I'm lucky, CEllContentClick works 3/10 times   
 
 
 try to write this instead.  
  Private zero dataGridView1_CellMouseClick (Object Sender, DataGridViewCellMouseEventArgsE) {if (e.RowIndex! = -1) {textBox1.Text = dataGridView1.Rows [e.RowIndex] .cs [0] Value.ToString (); } Other {textBox1.Text = ""; }}