Tell If A DataSet Or DataRow Is Empty?
Feb 23, 2012
After much convincing by other people, I have finally started trying to use ADO.NET instead of ADODB. Unfortunately, my lack of knowledge regarding these objects has left me broken in one area. I tried converting the area where I am checking for duplicate records to use ADO.NET by checking if a student filling out a form enters the same first name, last name, and program or major as another record in the database as per my instructions. Unfortunately, in the following code snippet, it is not behaving how I thought it should and I am unable to diagnose exactly where the problem might be just yet.
Here is the code in question:
Try
Dim orion As New SqlConnection(strConn)
Dim sqlCmd As System.Data.SqlClient.SqlCommand = New System.Data.SqlClient.SqlCommand(query, orion)
[Code]...
I probably should have mentioned also that it never flags an error despite there being 'duplicate' records in the database at this point.
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Aug 1, 2011
I have dataset like
<DATASET>
<SALES_DO_INDEPENDENT>
<SALES_DO_INDEPENDENT_ID>22</SALES_DO_INDEPENDENT_ID>
[Code]......
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Oct 9, 2009
I have a table with 3 rows and two columns (sid and number1). How can i bring a specific row with the SELECT? I use a textbox to give a criteria (sid). I guess it would be - SELECT number1 FROM Table2 WHERE sid = textbox1.text. How to pass that row into a dataset?
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Apr 2, 2011
How do i check if the dataset is empty? I wrote the following code:
[Code]...
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Oct 4, 2011
i have a dataset that takes results from a select to a sql database. the select returns rows and sometimes returns no rows. how can i check if the dataset has no rows from the select? [Code]
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Mar 10, 2011
Public Class ReceiptEntry
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Feb 14, 2009
im getting a image from my database to a data set. before i convert it to a proper picture i need to check whether ds.Tables("userDetails").Rows(0).Item("photo") is EMPTY or NOT. How should i write the if condition? <code>If ds.Tables("userDetails").Rows(0).Item("photo")<> ??? Then
Dim pictureData As Byte() = DirectCast(ds.Tables("userDetails").Rows(0).Item("photo"), Byte())
Dim picture As Image = Nothing
Using stream As New IO.MemoryStream(pictureData)
picture = Image.FromStream(stream)
End Using
[Code]...
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Apr 8, 2010
MsgBox(MyDataSet.mytable.Rows.Count)
Gives 0, why?
The table has data!
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Jun 3, 2011
I think this may be a usual issue but I am not able to find much info. There is a master customer database and a call log database at work. The call log database has two tables that are updated from the master database monthly. Now I am writing this vb frontend for the call log database and cannot figure out the update portion
For p = 0 To maxrowsC (currently around 1000 rows)
With myCommand.Parameters
.AddWithValue("@HEATSeq", dsCallLog.Tables("ConfigDS").Rows(p).Item(0))
[code].....
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Jan 13, 2012
I inherited a program that retrieves 3 datasets from our vendors' web services, converts it to a table and then merges the 3 tables before exporting into xml from the resulting combined table. The problem I am having is that when web services returns an empty dataset the program crashes in the attempt to create a table from the empty dataset.How do I modify this code to either create an empty table or recognize the empty dataset and skip around that particular table creation, merge and removal? There is always data in at least one of the datasets.
foreach (Branch branch in branches)
{
Console.WriteLine("Opening connection...");
Vendor.ws_ordersSoapClient VendorClient = new VendorInterface.Vendor.ws_ordersSoapClient();
[code]....
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May 17, 2009
I have a timer that runs every time by itself, and for the code the runs in it I would like to have it clear the dataset before it does anything, the timer runs every 10 seconds, so I tried to do dataset.clear but it would crash if the dataset had no values
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Apr 28, 2010
I have two datatables with similar structures that I want to make one existing row to be updated from another datatable.
For example, "tableA" has three columns: "one", "two", and "three"; with "one" being the primary key...
and "tableB" has three columns as well: "one", "two", and "three"; with "one" being the primary key.
Say there is a row on tableA that is different than a row on tableB (with a matching primary key). What I wanted to do, as efficiently as possible, is to take the that row from tableB and replace the one on tableA so it'll be modified.
I'm not sure if there's an easier way of doing that instead of using loops for setting the row's items.
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May 14, 2009
I have a DataGridView that has some columns with dates. It binds to an in-memory Datatable which gets loaded from an string array of data passed back from the backend Some of the rows returned have nulls for the date columns. Solution 1: If I define the Date column in the DataTable as "string" I can easily convert those nulls to empty strings and display it in the grid as empty strings (desired results). However, if the user clicks on the date column header to sort by date, it doesn't order the rows as you want. You get a purely string sort order. Not acceptable
[Code]...
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Jun 28, 2010
This must've have been asked before but I couldn't locate it. In a mixed code project (VB and C#) we were debugging some old Visual Basic code where a statement as follows could be found:
If Request.Params("xxx") <> "" Then
'do something
I considered this a bug as Request.Params could be null, in which case the statement would've become false which wasn't the idea. So I thought. I just found out, -- probably for the tenth time and I will keep forgetting -- that the following two statements are not equal, while Nothing in VB should be equal to null in C# (thought I):
if(String.Empty == null) // always false
If String.Empty = Nothing Then ' always true
Should I dismiss this as a typical Microsoft backward compatibility effort, or should I consider this a huge error in the VB.NET compiler? Does anybody know the Microsoftean opinion on this oddity?
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Aug 11, 2010
I have a array of strings and I am looping through them, but the string might be empty so I am trying this:
[Code]...
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Jun 29, 2010
I am trying to look at the next datarow in a datatable such as For Each dr in dt.rows
type = dr("Type")
type2 = dr("Type")
how can this be the next record? Of course, I would need to write an exception for the last record...
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Mar 16, 2011
I have a form with a datetimepicker. On load of the form, I set the value of the dtp from a datarow, with the following vb.net dtpRequiredDate.Value = dr.Item("RequiredDate")
This works fine. But when the form is loaded subsequent times in the session (form is not disposed on closing, shown as dialog), when presented to the user it just shows todays date, not that set by the above code. Stepping through code, the Onload code runs, and the dtp is set by the above code. Checking the value in debug at this point, the value of the dtp is correct. There is no further code in onload. But by the time it is displayed to the user shows todays date again. I have set a break point on the valuechanged of the dtp but it never fires again after it has been set by the above code.
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Oct 4, 2011
Can anyone explain exactly why Method 1 in the following code does not alter the DataTable where the other 2 methods do? It's obviously some kind of referencing issue, but why exactly?
[Code]...
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Mar 14, 2011
I am trying to add new operators (their name, category, password etc) to a dataset called "operators". (Though I could be adding any new datarow to it's relevent dataset). My program has allowed for the entry of all relevent data and filtered it to make sure it is acceptable. The user has pressed the UPDATE button and my program must now add the new datarow. (My code is in bold!).
I assume that I must first establish a connection to my database, so I start with :-
Dim Conn As New OleDbConnection(ConnectionString)
'I feel that something is needed here to reference OleDbDataAdapter - but what?
Conn.Open() 'Is this line needed?
Dim DSetOPERATORS As New DataSet("operators")
Dim DRowOPERATORS As DataRow = DSetOperators.Tables("operators").NewRow
[Code]....
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Sep 8, 2009
I am trying to get data out of a DataRow. Example:
Dim dr_simslot = dsFSC.tblSimSlot.Select("SimID=" & simID)
What I want is to say something like this:
Dim temp = dr_simslot.columnname
This is because I know only one record will be in the datarow.
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Mar 31, 2012
for each row as datarow in dt.rows
if row is last row in dt
msgbox("last row in datatable")
end if
next
how do i detect the last or first the row is in datatable
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Apr 19, 2012
I have a master DataTable that may contain some DataRow.RowError. I create multiple subset DataTables from my master DataTable using the DataView.ToTable method whenever the user wants to apply a filter or sort to the master table. However, the ToTable method does not transfer the RowError property of the data rows in the master table to my new subset table. So in order for me to transfer the row errors from my master table to my subset table I have to use a loop. The code below works fine, but with one exception (see below code).
Dim dtMaster As DataTable = Me.ds.Tables("Current")
Dim dtSubset As DataTable
Dim dv As DataView
[Code]....
Note, the primary key may contain 2 columns, however this is a rear case. If you know of any other solutions to transfer row errors let me know. I don't have to use the Find method.
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Oct 5, 2010
Code is in VB 2008,
In code i am using Datatable, using that select method datarow
Dim dt as New Datatable
Dim dr() as Datarow = nothing
[code].....
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Aug 9, 2009
Public Class frmVisitor
Private dbConnection As New OleDb.OleDbConnection()
'To add a DataAdapter
[Code]....
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Mar 15, 2010
When the user clicks an "Edit" button on my form, I want a box to come up which allows the user to edit a DataTable in a strongly-typed DataSet. What's the best way to do this?
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Jan 28, 2010
I have code running in the Datatable.ColumnChanging event in my dataset. This dataset underlies a form and conventional drag/drop controls are in place for data entry.when the event triggers and runs, I am running code in the form that checks the dataset.HasChanges property. It is showing False. But this is immediately after the ColumnChanging event has been triggered.Okay, I see by others posts and MSDN that .HasChanges will only be true after moving off the row with the changed column. I have also noted lots of discussion about the advanced binding property of DataSourceUpdate Mode, but that does not address this issue.I guess I can do this by checking the state of the row for the binding source. Just seems odd that the event behind the dataset can be triggered and that does not change the dataset.HasChanges property.
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May 14, 2012
I have tried everything I can to get beyond this error which shows below as <<<<< error here. It is trying to fill a dataset from a data adapter. If I change the SELECT statement to just SELECT * FROM xTable I get the correct number of records in each table. But anytime I try with a more complex statement I get the error message shown below which indicates System.Data.Common.DbDataAdapter.Fill(DataSet dataSet. I've completely erased all data and entered a new set of test data so I know there is no problem with relationships. Each table has primary key which is foreign key in other table. IS there something wrong with the Imports section: Imports System
[Code]...
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Aug 2, 2010
I'm using a LINQ query to translate data inside a DataTable object to be a simple IEnumerable of a custom POCO object.
My LINQ query is:
Dim dtMessages As DataTable
'...dtMessages is instantiated ByRef in a helper data access routine... '
Dim qry = From dr As DataRow In dtMessages.Rows
[code]....
However, the compiler is throwing a warning message under dr As DataRow with the message: Option Strict On disallows implicit conversions from 'Object' to 'System.Data.DataRow'.Why am I getting this error and what do I need to do to fix it? I would have thought that dtMessages.Rows returned a collection of type DataRow. Is this not correct?
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Jul 23, 2010
Private Function ColumnEqual(ByVal A As Object, ByVal B As Object) As Boolean
[Code]...
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Mar 15, 2012
I've VB.NET function that reads data from an Excel sheet and adds rows in a Datatable.
Private Function LoadDataToRows(ByVal TableName As DataTable, ByVal Header As System.Collections.Specialized.StringCollection) As Boolean
Dim HeaderDataExcel As String = String.Empty 'Data Header
[Code].....
But no data was add to the table, only emty rows.
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