C# - DataTable Deleting Old DataRows Before Inserting New Safe?
Apr 20, 2011
i have a many-to-many relationship table in a typed DataSet.For convenience on an update i'm deleting old relations before i'm adding the new(maybe the same as before).Now i wonder if this way is failsafe or if i should ensure only to delete which are really deleted(for example with LINQ) and only add that one which are really new.
In SQL-Server is a unique constraint defined for the relation table, the two foreign keys are a composite primary key. Is the order the DataAdapter updates the DataRows which RowState are <> Unchanged predictable or not?In other words: is it possible that DataAdapter.Update(DataTable) will result in an exception when the key already exists?
Now, I want to place the rows from foundrows into an empty data table.I did what I thought was the obvious but that only returns a bunch of rows with no data
how to make DataRows in a DataTable ReadOnly? You can set DataColumns ReadOnly, but not DataRows?
I'd like to bind a DataRow ReadOnly property to my DataGridViewRow ReadOnly property. So when my DataGridView displays the underlying DataTable, if the DataRow is ReadOnly then the DataGridViewRow would automatically be ReadOnly as well. how to do this other than the way I do it below?
For Each r As DataGridViewRow In Me.dgvCurrent.Rows If r.Cells("curAnalyteID").Value <> Me.cbxAnalyte.SelectedValue Then Me.dgvCurrent.Rows(r.Index).ReadOnly = True
I am trying to use the Select on a datatable and am having some trouble. I got it to find a match on rows in a datatable I fill with data in multiple columns. But I cannot seem to loop through the results to do something with it. Here is my code below. The table is already filled with data.
displaying it into Datagridview while inserting & deleting records in runtime..I insert records it into database using Access and delete but the datagridview not changes or update.my question is how can i update the datagridview while inserting records and deleting records.[code]
I have tried everything.but im not able to insert updat and delete the excel file..im able to connect the excel sheet.the connection also seems to be opened...here s my connection string:
Dim sConnectionString As String Const kunal = "C:" sConnectionString = "Provider=Microsoft.Jet.OLEDB.4.0;" & _
I am using VB.NET 2005. I need to know if I have some data values in a Datatable consisting 4 rows then is it possible to insert all these rows into a Table of a Database using a single INSERT statement?
Can you tell me how to syncronise the a DataSource when inserting a new row into a DataTable? [code]The user enters values in the Textboxes and clicks a save button.At that point I get a concurrency violation when using .Update to get the new row into the database.Can you tell me if I need to add any more code to synchronise everything?
I am a veteran programmer . However , I am new to visual basic 2010 . I am trying to create a database that ould store data within an access file *.mdb .I have created the database which includes multiple tables . moreover i have created app.config file using wizard and my database along with dataset appear in the visual basic 2010 project . moreover when i test the function insert in the dataset the function performs well and the output is correct and i can see the new row added in my access database . however when i try to use the ATLtableadapter.insertquery (ATL is a datatable in my database) function in my form (in view code) the row doesn't get added.
When i first used this function an exception occured was something like first system class exception data.dll something along that lines. . however , when i created a new oledb.oledbconnection and put its connection string as the one in windowsapplication1.my.settings.marketconnectionstring. and used the open comand to open a connection . the message stoppped appearing . however , the insertquery is not adding the row in my database still when i use it in the form.
insert a datatable into a mysql database? The way I'm doing it now is that I'm doing a for each-loop and inserting one and one row. Is there a better way to do this? I have like 500+ rows, so it takes a while to execute the loop.
I am facing a problem in inserting a datarow in the Ms access Database though visual basic application.The scenario is like this:I have a table named 'IssueReturn' for library management System. The table has these fields:
I've made DataGridView on my Form1(data from database i've made). And i did an event,when someone doubleclicks that row marker(that left side empty cell,when you mark all row) it opens up my Form2. I can't find a way to export those vallues(strings) in cells of selected row to my Form2,so i can use them there.
I'd like to partition my search results (which is in a DataTable) into groups of say 100 so the user navigates through them a chunk at a time.I thought I could bind an array of DataRows to a DataGridView as the DataSource but it just does not work. This is the code I tried
DataGridView.DataSource = (From r In DataTable.Rows Skip 200 Take 100).ToArray()
I'd like to stay away using the DataGridView's VirtualMode.
How to write xml foreach datarow in dataset? I have dataset with 5 record in table, i want write to xml file with 5 xml file. in one xml file have one record.
I want to set the DataSource Property of a listview and of a combobox to an array of datarows.
This is the Code:
[Code].....
The 'Name' column does exist, but the ComboBox shows only the type of each datarow not the contents! If I set the datasource to a datatable, the correct column is shown in the combobox/listview.
Mapping (Pulling) dataRows in a Column by Column manner as illustrated by the image below:I wanna use this method to import data in Column By Column choice method.
FROM: Represent Excel Columns with DataRows
TO: Represent SQL DataColumns
When I click IMport Button, I want it to pull all the dataRows in the Excel Columns and Transfer the Rows to The corresponding SQL DataColumns. The Columns are dynamic as the changes, so, it can't defined in a static manner.Please any idea on the Coding how to implement this, it is the last stage of my Project development.
I am using VS2005, using VB.Net?I just created a local copy of a project on my drive. The original copy is being worked on by another developer.I deleted the .vspscc & .scc files?However, everytime I make a change, I get the message that the file is locked, and exclusively checkout by another developer. How can I make changes to the project, that I have copied to my drive. I need to disconnect it from VSS.
I need to generate the IV and the KEY for an AES cryptography. I want to use the password and i am asking if it is safe to use the same password to get the Key and the IV?
I have an application that requires several threads, otherwise the main UI thread would end up frozen.i am after a little advice as i have not really don alot of threaded applications.
First Question;
I have a thread which handles data coming in from the serial port( this wil become much more complicated), is it safe to use a synclock on the serialport object : -
Unless the person actually gets into the source code they can't get the password am I right? Is it actually possible for them to get into the source code.
Basically what I'm asking is, is this safe and if not why not and how can it be made secure?
I'm calling a c++ dll I made myself - and it appears to be very VERY not thread safe!
I'm referencing it like this
<System.Runtime.InteropServices.DllImport("D:ACS DesktopdcxdcxDebugStringLibrary.dll", EntryPoint:="firstIndexOfKeyword", CallingConvention:=Runtime.InteropServices.CallingConvention.Cdecl)> _ Public Shared Function firstIndexOfKeyword(ByVal s As String, ByVal substr As String(), ByVal substrLength As Integer, ByVal markers As Integer()) As Integer End Function
Is there a way to make this IMPORT create something more threadsafe?
I'm dropping into this function - from several threads - to add an OBJECT to a dictionary collection
Private Delegate Function ReaderRegisterDelegate(ByRef rrFSOb As FSObject) As FSObject Private Function ReaderRegister(ByRef rrFSOb As FSObject) As FSObject Try[code].....
It's getting Object reference not set to an instance of an object.The FILEID key being added is F1. F2, F3 and F4 are in the dictionary. Seems like F1 arrived and the object wasn't properly setup. Or thread-slice caused me to see a partially messed with dictionary list?How can I make that a thread safe operation? I thought dropping out to the UI thread was a safe place to mess with code like this? Oddly enough I can go to the immediate window and do this
Let's say that I have a module that has a Queue in it. For other entities to Enqueue, they must go through a function:
[Code]....
If I have multiple threads running and they want to call InsertIntoQueue(), is this considered thread safe? I am under the impression that there is only one copy of the instructions in memory necessary to perform the InsertIntoQueue() function... which would lead me to think that this is thread safe. However, I wonder what happens when two threads attempt to run the function at the same time? Is this thread safe, and if not, how can I make it thread safe? (and What would be the performance implications regarding speed and memory usage)
im trying to create a safe type programme on visual basic, which has a set combination button which when first clicked opens up a box to allow a password to be entered, once entered the safe is locked until you enter the password and push a button to try the key,
