Serialize and Deserialize object and store in Hiddenfield using C# and JavaScriptSerializer in ASP.Net

Error is for this line.

smile says:

byte[] bytess = ((byte[])row.Cells[5].Text;

If you want to change in your code then it’s based on how you are getting byte value for image from database. If you are just storing value in any cell or control then it’s not convertable. Refer the below code for reference that how to store Byte data using property class and saved it in Hiddenfield and retrieve it when we require the byte data from hidden field using serialization and deserialization using the JSON JavaScriptSerializer.

HTML

<asp:GridView ID="GridView1" runat="server" HeaderStyle-BackColor="green" AutoGenerateColumns="false"
    Font-Names="Arial" Font-Size="11pt" AlternatingRowStyle-BackColor="#C2D69B"  OnRowDataBound="GridView1_RowDataBound">
    <Columns>
        <asp:TemplateField HeaderText="Image Name">
            <ItemTemplate >
                <asp:Label ID="lblValue" runat="server" Text='<%#Eval("Name") %>'></asp:Label>
                <asp:HiddenField ID="hfData" runat="server" />
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
</asp:GridView>

C#

public partial class ByteDataExample : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!this.IsPostBack)
        {
            // You can use any of method from below to bind grid 
            BindGridusingDataTable();           
            BindGrid();

            // To get Bytedata from hiddenfield using property Class
            ConvertStringDataToByte();
        }
    }

    private void BindGridusingDataTable()
    {
        List<Files> files = new List<Files>();

        string constr = ConfigurationManager.ConnectionStrings["ConStr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand("select Name, Data from tblFiles", con))
            {
                SqlDataAdapter sda = new SqlDataAdapter(cmd);
                DataTable dt = new DataTable();
                sda.Fill(dt);               

                for (int i = 0; i < dt.Rows.Count; i++)
                {
                    files.Add(new Files
                    {
                        Name = dt.Rows[i]["Name"].ToString(),
                        Data = (byte[])dt.Rows[i]["Data"]
                    });
                }
            }

            GridView1.DataSource = files;
            GridView1.DataBind();
        }
    }

    private void BindGrid()
    {
        string constr = ConfigurationManager.ConnectionStrings["ConStr"].ConnectionString;
        using (SqlConnection con = new SqlConnection(constr))
        {
            using (SqlCommand cmd = new SqlCommand())
            {
                cmd.CommandText = "select Name,Data from tblFiles";
                cmd.Connection = con;
                con.Open();
                List<Files> files = new List<Files>();
                using (SqlDataReader sdr = cmd.ExecuteReader())
                {
                    while (sdr.Read())
                    {
                        files.Add(new Files
                        {
                            Name = sdr["Name"].ToString(),
                            Data = (byte[])sdr["Data"]
                        });
                    }
                }

                GridView1.DataSource = files;
                GridView1.DataBind();

                con.Close();
            }
        }


    }

    protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.DataRow)
        {
            Files file = (e.Row.DataItem as Files);
            // Serialize file class object and save in hiddenfield hfData
            (e.Row.FindControl("hfData") as HiddenField).Value = new JavaScriptSerializer().Serialize(file);
        }
    }   

    private void ConvertStringDataToByte()
    {
        foreach (GridViewRow row in GridView1.Rows)
        {
            // Deserialize file class object which is saved in hiddenfield hfData
            Files File = new JavaScriptSerializer().Deserialize<Files>((row.FindControl("hfData") as HiddenField).Value);
            
            // Assign Byte data to byte object
            Byte[] bytes = File.Data;
        }
    }
}

// Class File 
public class Files
{
    public string Name { get; set; }
    public byte[] Data { get; set; }
}

Screenshot