How to generate grid wrting a quary in textarea

<textarea id="txtArea1" runat="server"> Enter text here... </textarea>

<asp:GridView runat="server" ID="gvDemo" AutoGenerateColumns="true">
<asp:GridView>

  SqlConnection con = new SqlConnection("ConnectionString");
  con.Open();
  SqlDataAdapter a = new SqlDataAdapter("SELECT * FROM TableName Where ColumnName= "+ txtArea1.Value, con);
  DataTable dt = new DataTable();
  a.Fill(dt);
  con.Close();
  gvDemo.DataSource= dt;
  gvDemo.DataBind();

Protected void btnClick(object sender, EventArgs e)
{
        cmd = new SqlCommand(txtarea.Text, con);
        dt = new DataTable();

        try
        {
            con.Open();
            da = new SqlDataAdapter(cmd);
            da.Fill(dt);
            if (dt.Rows.Count > 0)
            {
                GV.DataSource = dt;
                GV.DataBind();
            }
            
        }
        catch (Exception ex)
        {

        }
        finally
        {
            con.Close();
            con.Dispose();
        }
}