you can try like below
SqlCommand SqlCmd = new SqlCommand("Select * from Loanmaster where "+
"Id_Code LIKE '%"+ txt_Search.Text+ "%' or "+
"Customer LIKE '%"+ txt_Search.Text+"%' or "+
"Apprs_No LIKE '%"+ txt_Search.Text+ "%'", sqlCon);
But that is not secure. Use Parameterized sql statement, it is safe and you don't need to worry about quotes.
SqlCommand SqlCmd = new SqlCommand(@"Select * from Loanmaster where
Id_Code LIKE @searchkey or
Customer LIKE @searchkey or
Apprs_No LIKE @searchkey " , sqlCon);
SqlCmd.Parameters.AddWithValue("@searchkey", "%" + txt_Search.Text + "%");