How to add values to a temporary gridview without overwriting the first row values?

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Goodday!
I wanted to create a temporary gridview before saving.When I enter values on textboxs , click Add, then it will populate the gridview.

The problem:
1. When I have successfully added values for the first row, and add new values. It overwrites the first row values. I wanted to make the new values on the next row. Or just create a new row then show the new values that has been inputted from the textboxes.

Here is my code:

VB

Dim dt As New DataTable()

       dt.Columns.AddRange(New DataColumn(6) {New DataColumn("Code"), New DataColumn("Description"), New DataColumn("Specification"), New DataColumn("Availability"), New DataColumn("Storage Location"), New DataColumn("Quantity"), New DataColumn("Critical")})
       dt.Rows.Add(componentCodeTextbox.Text, DescriptionTextbox.Text, txt_specs.Text, cb_availability.SelectedItem, txt_location.Text, QuantityTextbox.Text, CriticalTextbox.Text)

       ViewState("dt") = dt
       TempGV.DataSource = TryCast(ViewState("dt"), DataTable)
       TempGV.DataBind()

End Sub

But has error in :
Dim dr As datarow = dt.NewRow()

ERROR: object null reference exception
do I have to add other code so that I could add new row?

Any help would be much appreciated. Thanks in advance.

Posted 9-Sep-14 21:17pm

NekoNao

Updated 9-Sep-14 22:22pm

v4

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Comments

Gihan Liyanage 10-Sep-14 3:24am

I am not familiar with vb.net but can you plz try this when adding new row to DT

Dim R As DataRow = dt.NewRow
R("Name") = txtName.Text
dt.Rows.Add(R)
DataGridView1.DataSource = dt

NekoNao 10-Sep-14 3:25am

okay will try.

NekoNao 10-Sep-14 3:35am

has error in dt.rows says "object null"

Gihan Liyanage 10-Sep-14 3:39am

You should create dt first
Dim dt As datatable = New DataTable()
Then add newdata row to dt.

Gihan Liyanage 10-Sep-14 3:47am

In your new code I can see the dt is on out of the scope where you have create the DT.

End If
Dim dr As datarow = dt.NewRow()

NekoNao 10-Sep-14 4:21am

its okay. i have solved the problem .

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NekoNao · Accepted Answer · 2014-09-09T22:22:00

This is my reference, and it solved my problem.

VB

Protected Sub BtnAddCourses_Click(sender As Object, e As EventArgs)
	Dim dt As datatable = New DataTable()
	If ViewState("ANYSTRING") Is Nothing Then
		dt.Columns.Add("COLUMNNAME1")
		dt.Columns.Add("COLUMNNAME2")
		dt.Columns.Add("COLUMNNAME3")
	Else
		dt = DirectCast(ViewState("ANYSTRING"), DataTable)
	End If
	Dim dr As datarow = dt.NewRow()
	dr("COLUMNNAME1") = TEXTBOX1.TEXT
	dr("COLUMNNAME2") = DROPDOWNLIST.SELECTEDVALUE
	dr("COLUMNNAME3") = TEXTBOX1.TEXT
	dt.Rows.Add(dr)
	ViewState("ANYSTRING") = dt
	GRIDVIEW.DataSource = dt
	GRIDVIEW.DataBind()
	GRIDVIEW.Visible = True
End Sub

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