On Gridview Row Updating The Data Is Not Updating ..please check the code and tell me y it was not updating

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ASP.NET

TextBox FirstName =(TextBox) gvExample.Rows[e.RowIndex].FindControl("txtFirstName");
TextBox LastName =(TextBox) gvExample.Rows[e.RowIndex].FindControl("txtLastName");
TextBox Title = (TextBox)gvExample.Rows[e.RowIndex].FindControl("txtTitle");
TextBox Country =(TextBox) gvExample.Rows[e.RowIndex].FindControl("txtCountry");
string query ="UPDATE USER_DETAILS SET LAST_NAME='" + LastName.Text + "',FIRST_NAME='" + FirstName.Text+ "',TITle='" + Title.Text+ "',COUNTRY='" + Country.Text+ "' where EMPLOYEE_ID='"+i+"'";


in query it is not taking the control text what should i do