急啊 asp 在逗号附近有语法错误
请问：这段代码 执行时会在“cmd1.ExecuteNonQuery();//执行修改数据信息的操作”提示“在逗号附近有语法错误”，是怎么回事呢？纠结了半天没有找到原因 很急呀 

public partial class Manage_AdminIntro : System.Web.UI.Page
{
  protected void Page_Load(object sender, EventArgs e)
  {

  try 
  {
  if (!IsPostBack)
  {
  Button2.Attributes.Add("onclick", "return confirm('您确定要修改该信息吗？')");
  SqlConnection sqlcon = new SqlConnection(ConfigurationManager.ConnectionStrings["connection"].ConnectionString);
  sqlcon.Open();
  string strselect = "select * from t_intro where introid = '1'";
  SqlCommand cmd = new SqlCommand(strselect, sqlcon);
  SqlDataReader dr = cmd.ExecuteReader();
  if (dr.Read())
  {
  FreeTextBox1.Text = dr["introduce"].ToString();
  }
  dr.Close();
  sqlcon.Close();

  }
  }
  catch{}
  }
   
   
  protected void Button2_Click(object sender, EventArgs e)
  {
  //不正确
  if (FreeTextBox1.Text == "")
  {
  Response.Write("<script>alert('简介内容不能为空！')</script>");
  return; //返回操作
  }
  else
  {
   
  SqlConnection sqlcon1 = new SqlConnection(ConfigurationManager.ConnectionStrings["connection"].ConnectionString);
  sqlcon1.Open(); 
  string StrSqls = "";
  StrSqls = "update t_intro set introduce=" + this.FreeTextBox1.Text + "where introid = '1'";
  SqlCommand cmd1 = new SqlCommand(StrSqls,sqlcon1);  
  cmd1.ExecuteNonQuery();//执行修改数据信息的操作
  sqlcon1.Close(); //关闭数据库连接
  Response.Write("<script>alert('简介编辑成功！')</script>");
  }
 
  }
   
}

------解决方案--------------------
StrSqls = "update t_intro set introduce='" + this.FreeTextBox1.Text + "' where introid = '1'";

------解决方案--------------------
StrSqls = "update t_intro set introduce=" + this.FreeTextBox1.Text + "where introid = '1'";
=》
StrSqls = "update t_intro set introduce='" + this.FreeTextBox1.Text + "' where introid = '1'";

------解决方案--------------------
字符串类型 sql里面要加上单引号 col = 'value'
一般提示xxx附近有语法错误，很大一部分情况是sql写的不对，把这条sql取出来仍数据库里试试就知道错哪了