Question

Is it possible to pass datatable object to another control object as parameter as following :

protected void DropDownlist2(string model)
{
     queryString = "Select modelcar from useritem where typecar=@model";

     SqlCommand cmd = new SqlCommand(queryString, useritemConnectionString1);
     cmd.Parameters.AddWithValue("@model", model);

     useritemConnectionString1.Open();

     DataTable dt = new DataTable();
     SqlDataAdapter ad = new SqlDataAdapter(cmd);
     ad.Fill(dt);

     if (dt.Rows.Count > 0)
     {
         DropDownList2.DataSource = dt;
         DropDownList2.DataBind();
     }

     useritemConnectionString1.Close();
     Button1(dt);
 }

 private void Button1_Click(DataTable dt)
 {   
     SqlDataReader dr = cmd.ExecuteReader();

     if(dr.HasRows)
     { 
         while (dr.Read()) 
         { 
              System.Web.UI.WebControls.Image imgControl = new System.Web.UI.WebControls.Image();
              HtmlGenericControl paraContainer = new HtmlGenericControl("p");
paraContainer.Controls.Add(imgControl);
              PlaceHolder1.Controls.Add(paraContainer);

              //Get Image Information
              imgControl.ImageUrl = dr["Image"].ToString();
          } 
    } 
    else  
        dr.Close();
} 

For some reason I get this error

button1_Click(System.data.datatable)is inacccessible due to its protection level

Answer 1

Make your Button1_Click method protected.

Check, is Button1 method called from DropDownlist2 the same as Button1_Click?

Update

In your dropdownlist selection event handler you should store your DataTable object in some field or property of your form. In event handler which corresponds to the your button click you should operate with this field.