Adding quantity if the product is exist in the DataGridView - vb.net

Question

Can someone help me with my problem?
The picture below shows the same item I inputted. What I want is I don't like to show duplicate items in DataGridView. If the same product record adds, then the new will not be showed, it just add the quantity when clicking the "Save" button. And I don't know how to code it I'm just new to vb.net. Can somebody help me how to do it?? It would be a big help for me if you do, thank you so much!
Below is my code for Save button:
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
initializeCon()
Dim found As Boolean = False
If (DataGridView1.Rows.Count > 0) Then
For Each row As DataGridViewRow In DataGridView1.Rows
If (Convert.ToString(row.Cells(1).Value) = dtDate.Text) And (Convert.ToString(row.Cells(2).Value) = txtProductCode.Text) AndAlso
(Convert.ToString(row.Cells(3).Value) = txtProductName.Text) Then
row.Cells(4).Value = Convert.ToString(txtQuantity.Text + Convert.ToInt16(row.Cells(4).Value))
found = True
End If
Next
If Not found Then
cmd = New SqlCommand("INSERT INTO tbl_productOrders VALUES('" & txtID.Text & "','" & dtDate.Text & "','" & txtProductCode.Text & "','" & txtProductName.Text & "'," & txtQuantity.Text & ");", con)
cmd.ExecuteNonQuery()
clrtxt()
SaveMsg()
Getdata()
End If
End If
End Sub

Answer 1

this is an axample to avoid duplicates while adding rows
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Dim exist As Boolean = False, numrow As Integer = 0, numtext As Integer
For Each itm As DataGridViewRow In DataGridView1.Rows
If itm.Cells(0).Value IsNot Nothing Then
If itm.Cells(0).Value.ToString = TextBox1.Text Then
exist = True
numrow = itm.Index
numtext = CInt(itm.Cells(1).Value)
Exit For
End If
End If
Next
If exist = False Then
DataGridView1.Rows.Add(New String() {TextBox1.Text, TextBox2.Text})
Else
DataGridView1.Rows(numrow).Cells(1).Value = CInt(TextBox2.Text) + numtext
End If
End Sub

Answer 2

There are two aspects to improve your program.
1. Make comparing products better
Since you need to check individual properties to find equal product, the better way is to overload == operator along with implementing IEquatable interface. You can read more here. When you do this, you can compare products with == operator: if (product1 == product2) { }. In this case three properties are being compared. If they all are the same, then two products are equal.
2. Make adding products to DataGridView easier
In order to make adding products to DataGridView easier, you need to leverage the handy binding mechanism in Windows Forms, which appeared in .NET Framework 2.0 - BindingSource. It acts like a medium between your data and controls. In order to make this class usable, you need to use another handy class - BindingList. You feed BindingList to BindingSource and assign BindingSource to DataSource property of DataGridView. After that you work only with BindingList collection (adding/removing/editing) - and all the propagation is done by BindinSource.
To summarize, here is the explanation and full code. Here you can download the project itself.
When you add product, the code first checks whether such product already exists in DataGridView (Add product button). Do note that we don't work with DataGridView directly - we work only with the collection. Thanks to enhancements, we can use LINQ here. If the product is not found, we add it to collection. If it's found, we just update the quantity.
If you need to update selected product data (Change quantity button), you only need to retrieve it from selected rows and use BoundDataItem - this is where our product is located. Then just update properties of product you need.
If you need to remove product (Delete product button), retrieve it from selected row and delete it from the collection.
Important! Do not forget to call Refresh() method on DataGridView after all taken actions in order to see the changes.
namespace WinFormsApp
{
public partial class Root : Form
{
private BindingList<Product> list = null;
private BindingSource bindingSource = null;
public Root() => InitializeComponent();
private void OnFormLoaded(object sender, EventArgs e)
{
// Our collection holding products
list = new BindingList<Product>();
// I've set up columns manually (with applied binding),
// so switch generating columns off.
dataGrid.AutoGenerateColumns = false;
// Disable adding new row
dataGrid.AllowUserToAddRows = false;
// Create our medium between grid and collection
bindingSource = new BindingSource { DataSource = list };
// Set binding
dataGrid.DataSource = bindingSource;
}
private void OnAddRecord(object sender, EventArgs e)
{
// Create new product
var new_product = new Product
{
Date = dtPicker.Value.ToShortDateString(),
Code = txtCode.Text,
Name = txtName.Text,
Quantity = npQuantity.Value
};
// No need to check individual properties here
// as == and IEquatable will do all the work.
// We can safely use LINQ here.
var p = list.FirstOrDefault(x => x == new_product);
if (p == null)
{
// Product is not found. Add it to list.
list.Add(new_product);
}
else
{
// Product is found. Update quantity.
p.Quantity += new_product.Quantity;
}
dataGrid.Refresh(); //Required to reflect changes
}
private void OnChangeQuantity(object sender, EventArgs e)
{
// Change quantity here.
var product = GetProduct();
if (product != null)
{
// Update product's quantity.
product.Quantity *= 2;
// Do not forget to refresh grid.
dataGrid.Refresh();
}
}
private void OnDeleteProduct(object sender, EventArgs e)
{
// Delete product here.
var product = GetProduct();
if (product != null)
{
// We need to delete product only from collection
list.Remove(product);
// Do not forget to refresh grid
dataGrid.Refresh();
}
}
// Retrieve product from selected row.
private Product GetProduct() =>
dataGrid.SelectedCells.Count == 0 ?
null :
dataGrid.SelectedCells[0].OwningRow.DataBoundItem as Product;
}
class Product : IEquatable<Product>
{
public string Date { get; set; }
public string Code { get; set; }
public string Name { get; set; }
public decimal Quantity { get; set; }
// Overload == operator
public static bool operator ==(Product firstProduct, Product secondProduct)
{
// Check for null on left side.
if (Object.ReferenceEquals(firstProduct, null))
{
if (Object.ReferenceEquals(secondProduct, null))
{
// null == null = true.
return true;
}
// Only the left side is null.
return false;
}
// Equals handles case of null on right side.
return firstProduct.Equals(secondProduct);
}
// Overload != operator (required when overloading == operator)
public static bool operator !=(Product firstProduct, Product secondProduct) =>
!(firstProduct == secondProduct);
// Implementing IEquatable<T> interface
public bool Equals(Product other)
{
// If 'other' is null, return false.
if (Object.ReferenceEquals(other, null))
{
return false;
}
// Optimization for a common success case.
if (Object.ReferenceEquals(this, other))
{
return true;
}
// If run-time types are not exactly the same, return false.
if (this.GetType() != other.GetType())
{
return false;
}
// Return true if the fields match.
return
Date == other.Date &&
Code == other.Code &&
Name == other.Name;
}
public override bool Equals(object obj) => this.Equals(obj as Product);
public override int GetHashCode() =>
Date.GetHashCode() + Code.GetHashCode() + Name.GetHashCode();
// Optional. For debugging purposes.
public override string ToString() =>
$"Date: {Date}, Code: {Code}, Name: {Name}, Quantity: {Quantity}";
}
}