Function is inaccessible due to its protection level

Question

Sir,

 

 I am in a login form  function in asp.net. I did a Login control to set a login module.

 

Here I  getting an error that  Function validate user  is inaccessible due to its protection level. why I getting this error. Here the html section screenshot:-

 

 And the C# coding is:-

 

Page Load Event

 

 

 

Function to set Validation