How to Display User info on Gridview based on who is login?

Have a look at roles and membership in ASP.Net -
https://www.asp.net/web-forms/tutorials/security/roles/creating-and-managing-roles-cs[^]
Understanding ASP.NET Roles and Membership - A Beginner's Tutorial[^]
http://msdn.microsoft.com/en-us/library/yh26yfzy%28v=vs.100%29.ASPX[^]

Make the query such a way that you don't have to write another one. For example,

SELECT * FROM User WHERE Email = @email and Password = @password

This would return all the records that has matched criteria.

Now, on Button_Click or any event of the control,

SqlCommand cmd= new SqlCommand("your query", connectionObject);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataTable dt = new DataTable();
da.Fill(dt);

userGridView.DataSource = dt;
userGridView.DataBind();

You can manipulate this code as per your requirements. This is just the basic idea how you can deal with your problem.

Hope this much is clear to you.
-KR