Dim dr As New DataRow??? [Resolved!]

While practicing some datasets today, I noticed that when I was to work with a datarow, I could not do this:

VB Code:

Dim dr As New DataRow

The tooltip said this:

Quote:

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'System.Data.DataRow.Protected Sub New(builder As System.Data.DataRowBuilder)' is not accessible in this context because it is 'Protected'.

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Can someone clarify the meaning of this to me? Also, why can I not declare a new datarow? Apprently, my OO concepts really aren't that good, since I fail to understand why this was done.

:afrog:

You have to create new records via the DataTable instance, I believe it is to ensure that each row has the correct column structure :)

To create a datarow obj do this :

VB Code:

Dim dr As DataRow=AnyDataset.Tables.Rows.NewDataRow (not sure of the last one)

Private members inside public classes gives this error after trying to instantiating it .

Because the DataRow object is part of a hierarchy of objects it does not have a default constructor, which is a constructor with no arguments. The DataRow must have information about the fields and table it is associated with so you would need to create a DataRowBuilder and pass that it if you choose that way. The normal way of creating a new row is from the DataTable object though and its NewRow method which will return a DataRow that is already associated with that table.

VB Code:

Dim ds As New DataSet
        Dim dr As DataRow = ds.Tables(0).NewRow

As Pirate mentioned.

Data row itself is not an independent .The DataRow and DataColumn objects are primary components of a DataTable.The kind of declaration tried is to declare a new row object which is wrong use.
The structure is like Data TableàData Column àData row

The error you are facing is because the base class data row does not allow it. That is why you get that exception.

OK, then can someone help me with this bit of code.

It's very simple. I've already populated my dataset. I am trying to populate fields in my form by using the elements of the datarow. Now, to do this, I obviously ened to set the datarow to a row in the dataset. So, I'm doing this:

VB Code:

dr = ds.Tables("Product").Rows.Find(CInt(lItem.ID))

After which I am using it like this:

VB Code:

txtID.Text = dr("ProductID").ToString
        txtName.Text = dr("ProductName").ToString

etc.

But, the dr = ds.Tables(...) line is showing an error:

Quote:

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Object reference not set to an instance of an object.

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Is something wrong with that line? I can upload the project if you'd like. It's a very simple DB project that uses the Northwind database.

Btw, lItem.ID is a class I've made, I doubt it's of any relevance here, as it's returning proper values. I've even tried replacing lItem.ID with 0 or 1, but it still won't work.

I'm uploading the sample here all the same. You can take a look at it.

MOTHER ****...

I hate it when I solve my own problems. :mad:

I misspelt products as product.

Thanks a lot for your inputs, guys.

This thread is resolved.