I want to show image through ajax by web method.

<asp:Image Height="200px" Width="200px" runat="server" ID="img_Product" CssClass="col-md-2 control-label labelfont"></asp:Image>            

Here is my ajax code,

$(document).ready(function () {       
    var productValue = <%=Session["StockId"] %>;
    var Data = JSON.stringify({ productId: productValue });
    $.ajax({
        type: "POST",
        url: "Image.aspx/GetImageByStockId",
        data: Data,
        dataType: "json",
        contentType: "application/json; charset=utf-8",
        success: function (data) {
            $("#img_Product").attr("src", data.d.Image);
            alert($("#img_Product").attr("src", data.d.Image));
        },
        error: function (xhr, status, error) {
            alert(error + status + xhr);
        }
    });        
});

Here is my webmethod code,

[WebMethod]
public static ImageModel GetImageByStockId(int productId)
{
    Services service = new Services();
    ImageModel imageModel = new ImageModel();
    string qrySelImage = "Select * from tbl_StockRunning where StockId = " + productId + "";
    DataTable dtSelImage = new DataTable();
    dtSelImage = service.GetDataTable(qrySelImage);
    if (dtSelImage.Rows[0]["DesignImage"].ToString() != "")
    {
        byte[] pic = Encoding.ASCII.GetBytes(dtSelImage.Rows[0]["DesignImage"].ToString());
        var data = (byte[])(dtSelImage.Rows[0]["DesignImage"]);
        imageModel.Image = "data:image/jpg;base64," + Convert.ToBase64String(data);
    }            
    return imageModel;
}

Now, when I run the code, it shows error i.e.
Error during serialization or deserialization using the JSON JavaScriptSerializer. The length of the string exceeds the value set on the maxJsonLength property. [track by console]