I am trying to add a value from DataTable dtUsers into a list UserLocations however I am getting the title error.
My code is:
Public UserLocations As New List(Of String())
For Each NewRow As DataRow In dtUsers.Rows
Dim seq As String = NewRow("SEQUENCE").Value.ToString
If CandRow("SQ") = NewRow("SQ") Then
UserLocations.Add(seq)
End If
Next
I don not understand why I cannot add a string to a list of strings.
How should I go about this?
Public UserLocations As New List(Of String)
For Each NewRow As DataRow In dtUsers.Rows
Dim seq As String = NewRow("SEQUENCE").Value.ToString()
If CandRow("SQ") = NewRow("SQ") Then
UserLocations.Add(seq)
End If
Next
Related
i'm in VS2008 Studio, i have this datagridview with multiple columns which the last column contains a date and time value.
lot's of rows are pretty the same except by they're date column.
what i wanted to do is to trim the whole datagridview duplicate rows except they're most recent ones based on they're date column.
i have sth like this:
Administrator,192.168.137.221,2,file://C:\WMPub\WMRoot\industrial.wmv , 07.Jul.2014 - 23:11:59
Administrator,192.168.137.221,2,file://C:\WMPub\WMRoot\industrial.wmv , 07.Jul.2014 -
21:11:59
Administrator,192.168.137.221,2,file://C:\WMPub\WMRoot\industrial.wmv , 07.Jul.2014 - 22:11:59
Administrator,192.168.137.221,2,file://C:\WMPub\WMRoot\industrial.wmv , 07.Jul.2014 - 20:11:59
Administrator,192.168.137.221,2,file://C:\WMPub\WMRoot\industrial.wmv , 07.Jul.2014 - 11:11:59
Everyone ,192.168.137.221,2,file://C:\WMPub\WMRoot\industrial.wmv , 07.Jul.2014 - 17:11:59
Everyone ,192.168.137.221,2,file://C:\WMPub\WMRoot\industrial.wmv , 07.Jul.2014 - 14:11:59
the output i want should be like this:
Administrator 192.168.137.221 2 file://C:\WMPub\WMRoot\industrial.wmv 07.Jul.2014 - 23:11:59
Everyone 192.168.137.201 2 file://C:\WMPub\WMRoot\industrial.wmv 07.Jul.2014 - 17:11:59
....
please consider "," as column seprators! (i dont know how to draw a table here, sorry again)!
i have this snippet that trim the duplicate lines in a datagridview but it lacks preserving the latest entry:
Public Function RemoveDuplicateRows(ByVal dTable As DataTable, ByVal colName As String) As DataTable
Dim hTable As New Hashtable()
Dim duplicateList As New ArrayList()
For Each dtRow As DataRow In dTable.Rows
If hTable.Contains(dtRow(colName)) Then
duplicateList.Add(dtRow)
Else
hTable.Add(dtRow(colName), String.Empty)
End If
Next
For Each dtRow As DataRow In duplicateList
dTable.Rows.Remove(dtRow)
Next
Return dTable
End Function
what should i do?
thanks in advance
Here is some code that illustrates the approach:
Dim dict As New dictionary(Of String, DataRow)
For Each dtRow As DataRow In dTable.Rows
Dim key As String = dtRow("column1") + "," + dtRow("column2") ' + etc.
Dim dictRow As DataRow = Nothing
If dict.TryGetValue(key, dictRow) Then
'check and update date
'you can skip this part, if your data is sorted
If dtRow("dateColumn") > dictRow("dateColumn") Then
dictRow("dateColumn") = dtRow("dateColumn")
End If
Else
dict.Add(key, dtRow)
End If
Next
In the end dict contains the rows you need, you can get them via dict.Values.ToArray()
EDIT: I found the error - dictRow should be dtRow in the above code (now fixed). Then it should work. Here is a full version of self contained example (console app), since I wrote it anyway - focus on RemoveDuplicates, the rest is just prepwork:
Sub Main()
Dim dt As New DataTable
With dt.Columns
.Add("PublishingPoint")
.Add("Username")
.Add("IP")
.Add("Status")
.Add("Req URL")
.Add("Last seen", GetType(Date))
End With
'this populates the initial data table, use your method
Dim _assembly As Assembly = Assembly.GetExecutingAssembly()
Dim _textStreamReader As New StreamReader(_assembly.GetManifestResourceStream("ConsoleApplication16.data.csv"))
While Not _textStreamReader.EndOfStream
Dim sLine As String = _textStreamReader.ReadLine().TrimEnd
If String.IsNullOrEmpty(sLine) Then Exit While
Dim values() As String = sLine.Split(",")
Dim newRow As DataRow = dt.NewRow
For iColumnIndex As Integer = 0 To dt.Columns.Count - 1
Dim columnName As String = dt.Columns(iColumnIndex).ColumnName
newRow.Item(columnName) = values(iColumnIndex)
Next
dt.Rows.Add(newRow)
End While
Console.WriteLine("Old count: " & dt.Rows.Count)
Dim newDt As DataTable = RemoveDuplicates(dt, "Last seen")
Console.WriteLine("New count: " & newDt.Rows.Count)
Console.ReadLine()
End Sub
Private Function RemoveDuplicates(dt As DataTable, colName As String) As DataTable
Dim keyColumnNames As New List(Of String)
Dim exceptColumnsHash As New HashSet(Of String)({colName})
For Each col As DataColumn In dt.Columns
Dim columnName As String = col.ColumnName
If Not exceptColumnsHash.Contains(col.ColumnName) Then
keyColumnNames.Add(columnName)
End If
Next
Dim dict As New Dictionary(Of String, DataRow)
For Each dtRow As DataRow In dt.Rows
Dim keyColumnValues As New List(Of String)
For Each keyColumnName In keyColumnNames
keyColumnValues.Add(dtRow.Item(keyColumnName))
Next
Dim key As String = String.Join(",", keyColumnValues)
Dim dictRow As DataRow = Nothing
If dict.TryGetValue(key, dictRow) Then
If dtRow(colName) > dictRow(colName) Then
dictRow(colName) = dtRow(colName)
End If
Else
dict.Add(key, dtRow)
End If
Next
Dim dtReturn As DataTable = dt.Clone
For Each dtRow As DataRow In dict.Values
dtReturn.ImportRow(dtRow)
Next
Return dtReturn
End Function
To make this code run, you need to manually add a file to the project and set build action to "Embedded resource".
I'm trying to populate a List using a DataTable, I have a for each loop that checks every row and adds the item to the list. But the code isn't working, I keep getting the error..
System.NullReferenceException: {"Object reference not set to an
instance of an object."}
-Data: {System.Collections.ListDictionaryInternal}
-HelpLink: Nothing -Inner Exception: Nothing
-TargetSite: {System.Collections.Generic.List`1[System.String] getListOfUsers()}
This is my code...
Function getListOfUsers() As List(Of String)
'Dim i As Integer = 0
Dim lUserNames As List(Of String) = Nothing
Dim dt As DataTable = getDataTable(db_Config, "SELECT * FROM tblUsers")
If dt.Rows.Count > 0 Then
Try
For Each dRowItem As DataRow In dt.Rows
'i = i + 1
'If IsDBNull(dt.Rows(0)("fldUserName").ToString) = False Then
' lUserNames.Add(dt.Rows(0)("fldUserName").ToString)
'End If
If dRowItem.Item("fldUserName").ToString <> "" Then
lUserNames.Add(dRowItem.Item("fldUserName").ToString)
End If
Next dRowItem
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End If
Return lUserNames
End Function
Currently lUserNames has not been initialized. You need to do this:
Dim lUserNames As New List(Of String)
You have declared the List, but you haven't initialized it.
So change
Dim lUserNames As List(Of String) = Nothing
to
Dim lUserNames As List(Of String) = New List(Of String)
Of course you would also get a NullReferenceException if getDataTable returns Nothing instead of an empty DataTable if tblUsers would be empty at If dt.Rows.Count > 0.
You're not initializing your List on line 4. It should be:
Dim lUserNames As List(Of String) = New List(Of String)()
Edit: apparently this is a bit of a CSharp'ism :) This also works:
Dim lUserNames As New List(Of String)
In vb.net If I have HashTable,key is integer and the value is a list of integers, how to append integers to the value of a given key,
I have tried it but each time I found the integer last added only, (the list only has the last item added).
Here is my code , where dt is DataTable object
Dim dt = report.getEvaluationReportByObjectiveGroupId(29)
Dim data As New Hashtable()
Dim dataEntry As DictionaryEntry
Dim res As String
For Each row As DataRow In dt.Rows
Dim strYear = row.Item("Year")
Dim strData = row.Item("EmpCount")
If data.ContainsKey(strYear) Then
Dim newCountArr As List(Of Int32) = DirectCast(data(strYear), List(Of Int32))
' newCountArr.AddRange(data(strYear))
newCountArr.Add(strData)
' data.Remove(strYear)
' data.Add(strYear, newCountArr)
Else
Dim countArr As New List(Of Integer)
countArr.Add(strData)
data.Add(strYear, countArr)
End If
' data.Add(strYear, strData)
Next row
I would suggest to use the strongly typed Dictionary(Of Int32, List(Of Int32)) instead, it works similar. But anyway, here's the HashTable approach:
Dim table = New Hashtable
Dim list = New List(Of Int32)
For i = 1 To 999
list.Add(i)
Next
table.Add(1, list)
' somewhere else you want to read the list for a given key (here 1) '
Dim list1 As List(Of Int32) = DirectCast(table(1), List(Of Int32))
list.Add(1000) ' add another integer to the end of the list '
' note: you don't need to add the list to the HashTable again '
Edit: Since you've posted your code, here's the corrected:
For Each row As DataRow In dt.Rows
Dim strYear = row.Field(Of Int32)("Year")
Dim strData = row.Field(Of Int32)("EmpCount")
Dim list As List(Of Int32)
If data.ContainsKey(strYear) Then
list = DirectCast(data(strYear), List(Of Int32))
Else
list = New List(Of Int32)
data.Add(strYear, list)
End If
list.Add(strData)
Next row
I'm trying to get the results from a Dynamic LINQ query into a DataTable. Trying to get the query directly into a DataTable gives me this error:
Unable to cast object of type 'System.Linq.EnumerableQuery`1[DynamicClass1]' to type 'System.Data.DataTable'.
My code is:
Dim query = tbl.AsEnumerable.AsQueryable.Select("new(it[""curr""] as Curry)")
Dim tbl As DataTable = query
Ive tried:
Dim query As IEnumerable(Of DataRow) = tbl.AsEnumerable.AsQueryable.Select("new(it[""curr""] as Curry)").Cast(Of DataRow)()
Dim tbl1 As DataTable = query.CopyToDataTable
but that gives me:
Unable to cast object of type 'DynamicClass1' to type 'System.Data.DataRow'.
Public Shared Function ConvertIEnumerableToDataTableFromProperties(Of T)(ByVal list As IEnumerable(Of T)) As DataTable
Dim table As New DataTable()
Dim fields() As PropertyInfo = GetType(T).GetProperties()
For Each field As PropertyInfo In fields
table.Columns.Add(field.Name, field.PropertyType)
Next
For Each item As T In list
Dim row As DataRow = table.NewRow()
For Each field As PropertyInfo In fields
row(field.Name) = field.GetValue(item)
Next
table.Rows.Add(row)
Next
Return table
End Function
I have a function that returns a list of account numbers as an Arraylist. I am trying to use each account as a command parameter in another sub routine to get more data about each account number. This only returns the data for the last account number in the arraylist. I need to use each account number, call the database, get the additional information and store ALL of the data into a Gridview (databind). Example: If I had 3 account numbers in my arraylist return 3 rows of data to the gridview. I am struggling with how to get ALL of the information for each value (account number) in the Arraylist. Can someone point me in the right direction?? I think this can be done but I am not certain if my approach is correct or not. Perhaps I need to create datatables that contain the additional information for each value passed via the arraylist....Any Ideas??
#jwatts1980 thanks for the comment: I will try to clarify. I have an arraylist of account numbers (and maybe this is where I am off track) I am trying to use the values in this ArrayList as command parameters in another call to a different table/file that returns more info on those accounts. I will provide a portion of the code to help clarify what it is I am attempting to do:
Private Function ReturnMultAccts(ByVal strAcct) As ArrayList
Dim acctsDetail As New ArrayList
Dim dsn As String = ConfigurationManager.ConnectionStrings.ConnectionString
Dim sql As String = "SELECT DISTINCT * FROM FILE WHERE ACCTNUM=?"
Using conn As New OdbcConnection(dsn)
Using cmd As New OdbcCommand(sql, conn)
conn.Open()
cmd.Parameters.Add("ACCTNUM", OdbcType.VarChar, 20).Value = strAcct
Dim rdrUsers As OdbcDataReader = cmd.ExecuteReader()
If rdrUsers.HasRows Then
While rdrUsers.Read()
acctsDetail.Add(Trim(rdrUsers.Item("ACCTNUM")))
End While
End If
rdrUsers.Close()
conn.Close()
End Using
End Using
This returns an Arraylist of Account Numbers (Lets say it is 3 acct numbers). I call this Function from another Sub:
Private Sub GetMoreAcctInfo(ByVal strAcct)
'Create New ArrayList
Dim MultAccts As New ArrayList
'Pass strAcct to Function to get Multiples
MultAccts = ReturnMultAccts(strAcct)
'Create the variable BachNum for the loop
Dim BachNum As String = MultAccts.Item(0)
For Each BachNum In MultAccts
'Get All of the necessary info from OtherFile based on the BachNum for BOS's
Dim dsn As String = ConfigurationManager.ConnectionStrings.ConnectionString
Dim sql As String = "SELECT ACCTNUM, BILSALCOD1, BILSALCOD2, BILSALCOD3, OTHACCTNUM FROM OtherFile WHERE OTHACCTNUM=?" 'Equal to the items in the arraylist
Using conn As New OdbcConnection(dsn)
Using cmd As New OdbcCommand(sql, conn)
conn.Open()
cmd.Parameters.Add("OTHACCTNUM", OdbcType.VarChar, 20).Value = BachNum
Using adapter = New OdbcDataAdapter(cmd)
Dim DS As New DataSet()
adapter.Fill(DS)
GridView1.DataSource = DS
GridView1.DataBind()
End Using
End Using
End Using
Next
End Sub
Hopefully this clarifies what I am attempting to do...??
To elaborate on my suggestion, you will need a list of strongly typed objects. You can add those items to the list, then bind the list to the GridView.
I'll start at the beginning. You know what kind of data is coming from your database: ACCTNUM, BILSALCOD1, BILSALCOD2, BILSALCOD3, and OTHACCTNUM. So you can use those to create an object.
Friend Class AccountClass
Private pACCTNUM As string = ""
Private pBILSALCOD1 As string = ""
Private pBILSALCOD2 As string = ""
Private pBILSALCOD3 As string = ""
Private pOTHACCTNUM As string = ""
Public Property ACCTNUM() As string
Get
Return pACCTNUM
End Get
Set(ByVal value as string)
Me.pACCTNUM = value
End Set
End Property
Public Property BILSALCOD1() As string
Get
Return pBILSALCOD1
End Get
Set(ByVal value as string)
Me.pBILSALCOD1 = value
End Set
End Property
Public Property BILSALCOD2() As string
Get
Return pBILSALCOD2
End Get
Set(ByVal value as string)
Me.pBILSALCOD2 = value
End Set
End Property
Public Property BILSALCOD3() As string
Get
Return pBILSALCOD3
End Get
Set(ByVal value as string)
Me.pBILSALCOD3 = value
End Set
End Property
Public Property OTHACCTNUM() As string
Get
Return pOTHACCTNUM
End Get
Set(ByVal value as string)
Me.pOTHACCTNUM = value
End Set
End Property
Sub New(ByVal ACCTNUM As string, ByVal BILSALCOD1 As string, ByVal BILSALCOD2 As string, ByVal BILSALCOD3 As string, ByVal OTHACCTNUM As string)
Me.ACCTNUM = ACCTNUM
Me.BILSALCOD1 = BILSALCOD1
Me.BILSALCOD2 = BILSALCOD2
Me.BILSALCOD3 = BILSALCOD3
Me.OTHACCTNUM = OTHACCTNUM
End Sub
End Class
Then you rework the GetMoreAcctInfo() routine to use it.
Private Sub GetMoreAcctInfo(ByVal strAcct)
'Create New ArrayList
Dim MultAccts As ArrayList
'Pass strAcct to Function to get Multiples
MultAccts = ReturnMultAccts(strAcct)
'Create the variable BachNum for the loop
Dim BachNum As String
'Create the list to bind to the grid
Dim AcctInfo As New Generic.List(Of AccountClass)
'create the dataset
Dim DS As DataSet
For Each BachNum In MultAccts
'Get All of the necessary info from OtherFile based on the BachNum for BOS's
Dim dsn As String = ConfigurationManager.ConnectionStrings.ConnectionString
Dim sql As String = "SELECT ACCTNUM, BILSALCOD1, BILSALCOD2, BILSALCOD3, OTHACCTNUM FROM OtherFile WHERE OTHACCTNUM=?" 'Equal to the items in the arraylist
Using conn As New OdbcConnection(dsn)
Using cmd As New OdbcCommand(sql, conn)
conn.Open()
cmd.Parameters.Add("OTHACCTNUM", OdbcType.VarChar, 20).Value = BachNum
Using adapter = New OdbcDataAdapter(cmd)
DS = New DataSet()
adapter.Fill(DS)
For Each t As DataTable In DS.Tables
For Each r As DataRow In t.Rows
AcctInfo.Add(new AccountClass(r("ACCTNUM"), r("BILSALCOD1"), r("BILSALCOD2"), r("BILSALCOD3"), r("OTHACCTNUM")))
Next
Next
End Using
End Using
End Using
Next
GridView1.DataSource = AcctInfo
GridView1.DataBind()
End Sub