title: Simple Insert, Update to SQL Server
body: <p>I have simple code like this</p>
  
  <pre><code> using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Web;
  using System.Web.UI;
  using System.Web.UI.WebControls;
  using System.Data.SqlClient;
  using System.Configuration;
  
  protected void Add_Click(object sender, EventArgs e)
              {
                  string strConnectionString = ConfigurationManager.ConnectionStrings["SqlServerCstr"].ConnectionString;
  
              SqlConnection myConnection = new SqlConnection(strConnectionString);
  
              string musteriadi = DropDownList1.SelectedIndex.ToString();
              string avukat = DropDownList2.SelectedIndex.ToString();
              string query = @"UPDATE AVUKAT SET MUSTERİ = @musteriadi, AVUKAT = avukat";
  
              SqlCommand myCommand = new SqlCommand();
              myCommand.Connection = myConnection;
  
              myConnection.Open();
              GridView1.DataSource = myCommand.ExecuteReader();
  
              GridView1.DataBind();
              GridView1.Visible = true;
  
              myConnection.Close();
          }
  </code></pre>
  
  <p>Where is the error? Simply, i want to add two column in my AVUKAT table,</p>
  
  <p>How can i solve it?</p>