Error when getting value from from datagrid

[Chair]

Hi,

I'd like to get the value of a column from a datagrid and insert that to a table. I get an error "Object reference not set to an instance of an object."

Here's my code:

Imports System.Data.SqlClient
Imports System.Data
Public Class Class1

Public Shared Sub insertrecord(ByVal query As String)
        con.Open()
        com.Connection = con
        com.CommandText = query
        com.ExecuteNonQuery()
        con.Close()

End Sub

Public Shared Sub readrecord(ByVal query As String)
        con.Open()
        com.CommandText = query
        com.Connection = con
        dr = com.ExecuteReader

    End Sub

End Class

Public Class FormRentals

Private Sub btnadd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnadd.Click

Dim indx As Integer = DataGridView1.Rows.Add()
                DataGridView1.Rows(indx).Cells(0).Value = (indx + 1).ToString
                DataGridView1.Rows(indx).Cells(1).Value = txtboxName.Text
                DataGridView1.Rows(indx).Cells(2).Value = FormatNumber(txtboxamt.Text,2).ToString

End Sub

Private Sub btnaddtocart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnaddtocart.Click

'This generates a primary key called ID that is set to be identity(1,1)
Class1.insertrecord("Insert into myTable(Name) values('" + txtboxName.Text + "')")

For x As Integer = 0 To (DataGridView1.Rows.Count() - 1)
     Class1.readrecord("Select * from myTable where Name='" + DataGridView1.Rows(x).Cells(1).Value.ToString + "'")
     If Class1.dr.Read() then
       Dim myID as Integer = Class1.dr("ID")
       Class1.con.Close
       Class1.insertrecord("Insert into amtdue(nameID,name,amount) values('" + myID.ToString + "','" + DataGridView1.Rows(x).Cells(1).Value.ToString + "','" + CType(DataGridView1.Rows(x).Cells(2).Value,Double).ToString + "')")
     End if
     Class1.con.Close

End Sub

End Class

The thing is -- when I look at table amtdue, everything is actually saved there. I just don't understand why I'm getting the error, and so I can't proceed with what I have to do after clicking the btnaddtocart button.

Would really appreciate any help. Thanks much in advance!

[AndreRet]

The error means that one of your objects has no reference. You need to make sure that every variable and object has been declared or referenced.:)

[Chair]

Hi, thanks for replying! But is it possible to have the data successfully saved to the table if there's an error like this?

The error is pointing to this line --

Class1.readrecord("Select * from myTable where Name='" + DataGridView1.Rows(x).Cells(1).Value.ToString + "

'")

but I see that it's reading myID fine because this line

Class1.insertrecord("Insert into amtdue(nameID,name,amount) values('" + myID.ToString + "','" + DataGridView1.Rows(x).Cells(1).Value.ToString + "','" + CType(DataGridView1.Rows(x).Cells(2).Value,Double).ToString + "')")

has been successfully inserted into the table.

I don't understand :=)

[AndreRet]

Class1.readrecord("Select * from myTable where Name='" + DataGridView1.Rows(x).Cells(1).Value.ToString + "

This part should not because you are missing an operator -

Class1.readrecord("Select * from myTable where Name='" + DataGridView1.Rows(x).Cells(1).Value.ToString + "'" 

' Added' and " at the end.

[Chair]

Oops sorry, it wasn't included within the CODE tags. Pls look at my code above, the operators trailed behind

[Chair]

Hi,

Do you think it's because there's something wrong with how I programmatically created my datagrid? I did it this way:

Private Sub FormNewReservation_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

DataGrid1.Columns.Add("Name", "Name")
DataGrid1.Columns.Add("AmtDue", "Amount Due")

Anyone please? Someone?

[Chair]

Sorry, wrong post above. Here's the correct one:

Hi,

Do you think it's because there's something wrong with how I programmatically created my datagrid? I did it this way:

Private Sub FormNewReservation_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

DataGridView1.Columns.Add("Name", "Name")
DataGridView1.Columns.Add("AmtDue", "Amount Due")

Anyone please? Someone?

[Chair]

Hi,

Just want to post here that I finally solved my problem. Instead of using this code,

For x As Integer = 0 To (DataGridView1.Rows.Count() - 1)

I needed to have these lines:

For Each row as DataGridViewRow In DataGridView1.Rows
                    If Not row.IsNewRow Then

Whew. I'm just so relieved.

[AndreRet]

I'm sorry I could not attend to your final solution, was up to my neck in work. Well done on solving this yourself though, this is what makes you a better developer and ensure that you understand the code as well.:) Some kudos for solving this on your own.;)

Please mark this as solved, found at the bottom of this page, thanks.

Happy coding.:)