ASP.NET Web-Form C# Specified cast is not valid -

i new asp.net , i'm trying make webshop. problem when try execute method, error.

i'm wondering if problem in sql tables? here's method produces error

    public list<product> productread(int product_id)             {                  idatareader data = sqlhelper.executereader(con, "product_read", product_id);                 list<product> prod = new list<product>();                 while(data.read())                 {                     product pr = new product();                     pr.product_id=(int)data["product_id"];                     pr.product_name=data["product_name"]as string;                     pr.product_description=data["product_description"]as string;                     pr.product_image =(char)data["product_image"];                     pr.product_price=(int)data["product_price"];                     pr.product_count=(int)data["product_count"];                     prod.add(pr);                 }                 return prod;             } 

and how execute above method:

    list<product> pr = db.instance.productread(12);                 if (pr != null)                 {                     foreach (product product in pr)                     {                         panel prpanel = new panel();                         imagebutton imgb = new imagebutton();                         label lbname = new label();                         label lblprice = new label();                          imgb.imageurl = "~/images/" + product.product_image;                         imgb.postbackurl = "~/home.aspx?id=" + product.product_id;                         lbname.text = product.product_name;                         lblprice.text = "$" + product.product_price;                          prpanel.controls.add(imgb);                         prpanel.controls.add(new literal { text = "<br/>" });                         prpanel.controls.add(lbname);                         prpanel.controls.add(new literal { text = "<br/>" });                         prpanel.controls.add(lblprice);                         pnlproducts.controls.add(prpanel);                     }                   }                 else                 {                     pnlproducts.controls.add(new literal { text = "no product found !" });                 } 

and error:

specified cast not valid 

from line in code

imgb.imageurl = "~/images/" + product.product_image; 

it looks you're expecting data["product_image"] of type string, perhaps change cast to:

pr.product_image =(string)data["product_image"]; 

however, more useful add lines:

var productimage = data["product_image"]; type productimagetype = productimage.gettype(); 

you debug , step through code , find actual type of data["product_image"]. amend cast in broken line whatever needs be.