Object reference not set to an instance of an object

Emmmanuel FIADUFE

1y1.1kASP.NET

Hello Team.

I have purchase table and purchaseItem table with thier respective modelView. and in my ajax post request I keep getting this error, Object reference not set to an instance of an object. kindly assist.

function SavePurchases()
{
debugger;

var purchaseModel = new Object();
var ListOfPurchaseItemsViewModel = new Array();
purchaseModel.PurchaseID = $.trim($('#PurchaseID').val() + '--' + $('#SelectSupplier').val()),
purchaseModel.Date = $('#InvocingDate').val().trim(),
purchaseModel.SupplierID = $('#SelectSupplier').val(),
purchaseModel.Amount = $('#Amount').val(),
purchaseModel.Discount = $('#Discount').val(),
purchaseModel.Tax = $('#Tax').val(),
purchaseModel.GrandTotal = $('#GrandTotal').val(),
purchaseModel.IsPaid = $('#Payment').is(":checked") ? 1 : 0,
purchaseModel.Description = $('#Description').val(),

$("#orderItems").find("tr:gt(0)").each(function () {
var PurchaseItemsViewModel = {};
debugger;
//PurchaseItemModel.ItemID = parseFloat($(this).find("td:eq(0)").text());
PurchaseItemsViewModel.ItemName = String($(this).find("td:eq(0)").text());
PurchaseItemsViewModel.Batch = parseFloat($(this).find("td:eq(5)").text());
PurchaseItemsViewModel.Qty = parseFloat($(this).find("td:eq(2)").text());
PurchaseItemsViewModel.CostPrice = parseFloat($(this).find("td:eq(3)").text());
PurchaseItemsViewModel.SellingPrice = parseFloat($(this).find("td:eq(4)").text());
PurchaseItemsViewModel.Expiry = Date($(this).find("td:eq(6)").html());

//var dateText = $(this).find("td:eq(6)").text().trim();
//var parts = dateText.split('/');
//var formattedDate = new Date(parts[2], parts[1] - 1, parts[0]); // Month is 0-based
//PurchaseItemModel.Expiry = formattedDate;

// Assuming Moment.js is included in the project
//var dateText = $(this).find("td:eq(6)").text().trim();
//var formattedDate = moment(dateText, "DD/MM/YYYY").format("YYYY-MM-DD");
//PurchaseItemModel.Expiry = formattedDate;

ListOfPurchaseItemsViewModel.push(PurchaseItemsViewModel);
});
ListOfPurchaseItemsViewModel.purchaseModel = ListOfPurchaseItemsViewModel;
//post data to server
$.ajax({
async: true,
contentType: "application/json; charset=utf-8",
type: "POST",
dataType: "JSON",
url: "/PurchaseEntry/SavePurchase",
data: JSON.stringify(purchaseModel),
success: function (d) {
//check is successfully save to database
if (d.status == true) {
//will send status from server side
alert('Successfully done.');
location.reload(true);
//clear form
purchaseItems = [];
$('#PurchaseID').val('');
$('#InvocingDate').val('');
$('#SelectSupplier').val('0');

}
else {
alert('Failed');
}
$('#submit').val('Save');
},
error: function () {
alert('Error. Please try again.');
$('#btnSubmit').val('Save');
}
});

}

public ActionResult SavePurchase(PurchaseItem purchaseModel)
{
var result = false;
try
{

tblPurchase objPurchase = new tblPurchase();
if (purchaseModel.tblPurchase.PurchaseID > 0)
{
objPurchase = objASPNETPHARMACYDBEntities.tblPurchases.Where(x => x.PurchaseID == purchaseModel.PurchaseID).FirstOrDefault();
}else
{
objPurchase.Date = purchaseModel.tblPurchase.Date;
objPurchase.SupplierID = purchaseModel.tblPurchase.SupplierID;
objPurchase.Amount = purchaseModel.tblPurchase.Amount;
objPurchase.Discount = purchaseModel.tblPurchase.Discount;
objPurchase.Tax = purchaseModel.tblPurchase.Tax;
objPurchase.GrandTotal = purchaseModel.tblPurchase.GrandTotal;
objPurchase.IsPaid = purchaseModel.tblPurchase.IsPaid;
objPurchase.Description = purchaseModel.tblPurchase.Description;
if (purchaseModel.tblPurchase.PurchaseID <= 0)
objASPNETPHARMACYDBEntities.tblPurchases.Add(objPurchase);
objASPNETPHARMACYDBEntities.SaveChanges();
purchaseModel.PurchaseID = purchaseModel.PurchaseID;
}
tblPurchaseItem updatePurchase = new tblPurchaseItem();
if (purchaseModel.PurchaseItemID > 0)
{
updatePurchase = objASPNETPHARMACYDBEntities.tblPurchaseItems.Where(x => x.PurchaseItemID == purchaseModel.PurchaseItemID).FirstOrDefault();
}
else
{
updatePurchase.PurchaseID = purchaseModel.PurchaseID;
updatePurchase.ItemID = purchaseModel.ItemID;
updatePurchase.Batch = purchaseModel.Batch;
updatePurchase.Qty = purchaseModel.Qty;
updatePurchase.CostPrice = purchaseModel.CostPrice;
updatePurchase.SellingPrice = purchaseModel.SellingPrice;
updatePurchase.Expiry = purchaseModel.Expiry;

}
if (purchaseModel.PurchaseItemID <= 0)
{
objASPNETPHARMACYDBEntities.tblPurchaseItems.Add(updatePurchase);
}
objASPNETPHARMACYDBEntities.SaveChanges();
result = true;
}
catch (Exception ex)
{
throw ex;
//return Json(new { result = true, message = "Purchase fails to save!" }, JsonRequestBehavior.AllowGet);
}
return Json(new { result = true, message = "Purchase successfully saved!" }, JsonRequestBehavior.AllowGet);
}

8 Replies

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Tuhin Paul1y ago

Accepted answer

update the JS code like this:

function SavePurchases() {
    var purchaseModel = {
        tblPurchase: {
            PurchaseID: $.trim($('#PurchaseID').val() + '--' + $('#SelectSupplier').val()),
            Date: $('#InvocingDate').val().trim(),
            SupplierID: $('#SelectSupplier').val(),
            Amount: parseFloat($('#Amount').val()),
            Discount: parseFloat($('#Discount').val()),
            Tax: parseFloat($('#Tax').val()),
            GrandTotal: parseFloat($('#GrandTotal').val()),
            IsPaid: $('#Payment').is(":checked") ? 1 : 0,
            Description: $('#Description').val()
        },
        PurchaseItems: []
    };

    $("#orderItems").find("tr:gt(0)").each(function () {
        var purchaseItem = {
            ItemName: $(this).find("td:eq(0)").text(),
            Batch: parseFloat($(this).find("td:eq(5)").text()),
            Qty: parseFloat($(this).find("td:eq(2)").text()),
            CostPrice: parseFloat($(this).find("td:eq(3)").text()),
            SellingPrice: parseFloat($(this).find("td:eq(4)").text()),
            Expiry: $(this).find("td:eq(6)").text()
        };
        purchaseModel.PurchaseItems.push(purchaseItem);
    });

    $.ajax({
        async: true,
        contentType: "application/json; charset=utf-8",
        type: "POST",
        dataType: "JSON",
        url: "/PurchaseEntry/SavePurchase",
        data: JSON.stringify(purchaseModel),
        success: function (d) {
            if (d.result == true) {
                alert(d.message);
                location.reload(true);
            } else {
                alert('Failed: ' + d.message);
            }
        },
        error: function (xhr, status, error) {
            alert('Error: ' + xhr.responseText);
        }
    });
}

let's update your C# action method:

public class PurchaseViewModel
{
    public tblPurchase tblPurchase { get; set; }
    public List PurchaseItems { get; set; }
}

public class PurchaseItemViewModel
{
    public string ItemName { get; set; }
    public float Batch { get; set; }
    public float Qty { get; set; }
    public float CostPrice { get; set; }
    public float SellingPrice { get; set; }
    public string Expiry { get; set; }
}

[HttpPost]
public ActionResult SavePurchase(PurchaseViewModel purchaseModel)
{
    if (purchaseModel == null || purchaseModel.tblPurchase == null)
    {
        return Json(new { result = false, message = "Invalid data received." }, JsonRequestBehavior.AllowGet);
    }

    try
    {
        tblPurchase objPurchase = new tblPurchase();
        
        // Map properties from purchaseModel.tblPurchase to objPurchase
        objPurchase.Date = purchaseModel.tblPurchase.Date;
        objPurchase.SupplierID = purchaseModel.tblPurchase.SupplierID;
        objPurchase.Amount = purchaseModel.tblPurchase.Amount;
        objPurchase.Discount = purchaseModel.tblPurchase.Discount;
        objPurchase.Tax = purchaseModel.tblPurchase.Tax;
        objPurchase.GrandTotal = purchaseModel.tblPurchase.GrandTotal;
        objPurchase.IsPaid = purchaseModel.tblPurchase.IsPaid;
        objPurchase.Description = purchaseModel.tblPurchase.Description;

        objASPNETPHARMACYDBEntities.tblPurchases.Add(objPurchase);
        objASPNETPHARMACYDBEntities.SaveChanges();

        foreach (var item in purchaseModel.PurchaseItems)
        {
            tblPurchaseItem purchaseItem = new tblPurchaseItem
            {
                PurchaseID = objPurchase.PurchaseID,
                ItemID = GetItemIdByName(item.ItemName), // You need to implement this method
                Batch = item.Batch,
                Qty = item.Qty,
                CostPrice = item.CostPrice,
                SellingPrice = item.SellingPrice,
                Expiry = DateTime.Parse(item.Expiry)
            };

            objASPNETPHARMACYDBEntities.tblPurchaseItems.Add(purchaseItem);
        }

        objASPNETPHARMACYDBEntities.SaveChanges();

        return Json(new { result = true, message = "Purchase successfully saved!" }, JsonRequestBehavior.AllowGet);
    }
    catch (Exception ex)
    {
        return Json(new { result = false, message = "Error: " + ex.Message }, JsonRequestBehavior.AllowGet);
    }
}

// Implement this method to get ItemID by ItemName
private int GetItemIdByName(string itemName)
{
    // Query your database to get the ItemID based on the ItemName
    // Return the ItemID
    throw new NotImplementedException();
}

Modification done are as follows:

Created a `PurchaseViewModel` that matches the structure of the data sent from the client.
Updated the JavaScript code to properly structure the data before sending it to the server.
Modified the C# action method to handle the new data structure and perform proper null checks.
Simplified the purchase saving process by always creating a new purchase instead of updating an existing one.

You need to implement the `GetItemIdByName` method to retrieve the correct `ItemID` based on the `ItemName` you're receiving from the client.

Emmmanuel FIADUFE1y ago
This is my model

public class PurchaseItem
{
[Key]
public int PurchaseItemID { get; set; }
public int PurchaseID { get; set; }
public int ItemID { get; set; }
public string Batch { get; set; }
public string ItemName { get; set; }

[Range(0, 1000000, ErrorMessage = "Not an acceptable Quantity!")]
public int Qty { get; set; }

[Range(0.00, 99999999.99)]
public decimal CostPrice { get; set; }
public decimal SellingPrice { get; set; }

[DisplayFormat(DataFormatString = "{yyyy-MM-dd}", ApplyFormatInEditMode = true)]
public string Expiry { get; set; }

public virtual Item Item { get; set; }
public virtual PurchaseViewModel tblPurchase { get; set; }
}
0
Emmmanuel FIADUFE1y ago
Hello Mr Paul.

when I implement this method and I tried to save the data, the data got save only in the purchase table whiles purcahseItem table remain empty.

I change the model content and the JS structure as you said but this error keeps coming, reference not set to an instance of a string. Parameter name:s,

What could be the cause of this error.
0
Emmmanuel FIADUFE1y ago
I'm wondering if this error could occur as a result of the date format which is not working properly
0
Emmmanuel FIADUFE1y ago
Hello Mr Paul.

when I implement this method and I tried to save data, the data got save only in the purchase tabel whiles purcahseItem item table remain empty and this the error message that came.

// Query your database to get the ItemID based on the ItemName // Return the ItemID

this is my method for calling ItemId based on the ItemName.

private int GetItemIdByName(string itemName)
{
try
{
// Query your database to get the ItemID based on the ItemName
// Return the ItemID

var itemId = (from item in objASPNETPHARMACYDBEntities.tblItems
where item.ItemName == itemName
select item.ItemID).FirstOrDefault();

return itemId;
}
catch (Exception)
{
// Log the exception
// ...

// Re-throw the exception or return a default value
throw new NotImplementedException();
}
}
0
Emmmanuel FIADUFE1y ago
Thank you Mr Paul for your swift response, I will update the code accordingly and revert
0
Tuhin Paul1y ago
Check below the flowchart. hope it might help.

+1
Tuhin Paul1y ago
The `PurchaseItem` model you're receiving doesn't match the structure of the data you're sending from the client.
In your JavaScript code, you're creating a `purchaseModel` object, but you're not including the `ListOfPurchaseItemsViewModel` in it.
The server is expecting a `PurchaseItem` object, but it's receiving just the `purchaseModel` without the list of items.
+1