Synchronize Datatable And DataView For Read / Write Operations?
May 5, 2010
I have application in .net 2.0 in which I have a DataTable object globally in my application and have different dataviews in whole application.
When an action performed i have create many threads lets say 5 in which data is read from different dataview, meanwhile while 2/3 threads are reading data(not all 2 more left to read data) a thread write data in datatable. So we get exceptions like "Enumeration update" or "parameter not null" type.
I have use ReadWriteLock for this but do not find any luck it gets stop on ReaderWriterLock.AcquireWriterLock().
I have a multi-threaded application with several datasets that are read/written to from a couple threads. I have read that datasets can handle multiple readers and one writer. I have synclocks around all dataset writes and no synchronization around reads. I am experiencing random "Index was outside the bounds of the array." exceptions where a dataset item is in a conditional statement, for example:
I am currently working on an application which requires reading, writing and modifying data from a TEXT file. I have searched a lot but was not able to find a simple way to achieve this. I have to use a standard VB form with textboxes for ths text file opearations. s
I am currently working on an application which requires reading, writing and modifying data from a TEXT file. I have searched a lot but was not able to find a simple way to achieve this. I have to use a standard VB form with textboxes for this text file operations.
If want to do a DataView.Find on a DataTable that is already 'ORDERED' by the Column I am seaching, so a DataView.SORT should not be necessary, but it throws an Exception if I don't give a .sort command before the .find command. Is there any way to avoid this apparant duplication ? and speed up the search time. Its a very large table - 1 million rows. I am using VB 2010
I have a datatable and I apply a filter to the defaultview.rowfilter property of that datatable. If I then loop through the rows collection of the datatable, will I only be able to see those rows that the filter applies to, or will it loop through all the rows?
I'm looking at an old web app I wrote and it is taking about an hour to read 4500 records from a DataTable so it can write them to a CSV file.
The DataTable contains... 376 columns
At least, I think that's what Excel's NL column converts to. I just looked up the column count now and had no idea there were so many. Our software vendor hasn't realized the value of dynamic sql statements for this process, so every software "upgrade" just keeps adding more columns rather than only selecting the ones needed. I cannot alter the SQL statement that generates the data Depending on the data type, the data needs to be formatted in a specific format Data does contains special characters, such as commas The slow part is reading the data. Getting the data from the SQL server and writing it to a CSV is fast.
Here's the code. Forgive the mess, I wrote it back when I didn't know what I was doing and when I still was working in VB
Function ReadDataTableForCSV(dt as DataTable) Dim sb = New StringBuilder() Dim dataTypes As New Dictionary(Of String, Integer)
I start by looping through a string array, parsing out the strings I want and saving them to a temp table (I believe this part is working).Then, I take a DataView of the tale to get only the unique values from the rows.Then, things get messy, I need to get these unique values into my dataset. I been trying to do so using the DataView and also by passing the View to a new temp table then looping the values into the DataSet
I want to find a particular ID in a DataTable, I am using a DataView to filter the results, but how do I know which row in the original table the filter view corresponds to? Any ideas? In know I could use LINQ but I don't think this would help either?
VB2010, MySql I have a dataview generated from a datatable using a rowfilter.I have event handlers listening to the dataview.listchanged event. To keep the datatable (in memory) in sync with the mysql database (on a remote server), i issue datadapter.fill commands every now and then, the objective being that only the changed rows in the datatable (as a result of the fill) would generate a listchanged event on the dataview.To my surprise the dataview_listchanged event fires after refresh by the dataadapter.fill method, however the ListChangedType it gives is: ListChangedType = reset. I would have expected a ListChangedType.ItemChanged for every changed datarow.Since the dataview is used to populate a large storage yard, i am now forced to repopulate the whole storage yard, which is a time consuming business.Is there a way to only generate DataView.ListChanged events for rows in the datatable that are actually changed by the datadapter.fill method?
For my app users can enter a SELECT statement themselves. This can be any select statement at all, it will be mainly used for creating a quick view e.g. SELECT * from table1 LEFT OUTER JOIN table2 on table1.id = table2.id.
Whatever this select statement maybe I load it into a datatable (after checking for no nasty stuff of course) in vb.net. I want to know the table names so I can query the database again for validation purposes on things like datatypes etc.
da.SelectCommand = New SqlCommand(sqlStatement, tempDB.Connection) da.MissingSchemaAction = MissingSchemaAction.AddWithKey dt = New DataTable da.Fill(dt)
For my app users can enter a SELECT statement themselves. This can be any select statement at all, it will be mainly used for creating a quick view e.g. SELECT * from table1 LEFT OUTER JOIN table2 on table1.id = table2.id.Whatever this select statement maybe I load it into a datatable (after checking for no nasty stuff of course) in vb.net. I want to know the table names so I can query the database again for validation purposes on things like datatypes etc.
da.SelectCommand = New SqlCommand(sqlStatement, tempDB.Connection) da.MissingSchemaAction = MissingSchemaAction.AddWithKey dt = New DataTable da.Fill(dt)
im trying to select some rows based on a criteria, i was wondering is it faster if i create a dataview (based on the criteria) and then loop through the view? or should i loop through the entire datatable and check the criteria manually.
i guys, Ive been stuck on this problem for awhile now I need to read an XML document into a dataview object.At the moment I am reading the Xml into a dataset
Public Function GetDataSet() As DataSet Dim ds As DataSet ds = New DataSet
I have a page which lists all the files in a particular folder (all PDFs), using a data-table and gridview. I'm currently sorting this table by the filename (by using a dataview), which isn't that helpful, and I want the gridview of files sorted by the file created or file modified date (as recorded in Windows). If that's not possible, a second option would be to extract the date from the file name string (no problem doing that), and sort the dataview/datatable or gridview based on that.
I got a problem with dataview that get data from datatabel (Col1 : ID,Col2: Time) and I'm sorting by Time in desc ... when the values for example {40.21,80.21,70.25,25.2} the dataview sorting them as I need but when one of values goes above 100 for example {40.21,80.21,100.25,25.2} the dataview always sort the highest number is the buttom, I don't know why ..
This is a sample code
Dim dt As New DataTable dt.Columns.Add("ID") dt.Columns.Add("Time") [CODE]...
This is what I've got so far.I'm needing to access a data table on the server (tblStateCodes), loop through each line and write the contents to a local file (text or CSV).I've trolled the internet but it seems that there are many different examples which have confused me even more.
Imports System.Data.SqlClient Imports System Imports System.IO[code].....
My google skills have failed me on this, so I'm hoping that someone could point me in the right direction.I have a windows forms application that writes data to a datatable, which is then manipulated & saved into an access database. I am now looking to retrieve the data and write it out into a word document.
I'm getting a set of data by a datareader and assigning to a string. Now I need to fill the datatable columns with the Query fields. The datatable is connected to a grid to display the filled data. query is : strSQL = "SELECT EmpCode,EmpID,EmpName FROM dbo.Employee" Datatable columns are EmpCode,EmpID,EmpName. I need to read the query and assigned to the columns of datatable and fill the table. Me.DtShifts.Tables("NonAllocated").Clear() Me.DtShifts.Tables("NonAllocated").Load(dr)
I have a folder called movies. In this folder is a collection of different movies each in their own folder with their own xml file called movie.xml.I would like to extract lets say the localtitle and aspectratio from each movie xml and send to Excel. What code would I need to achieve this?So far I have the attached code which reads only one file and it is directly from the xml outside of a folder.
Is there anybody out here in the VB, C# 2008 world that can direct me in the right direction? I do not want anything that has todo with c/C++or Direct Draw. When converting, there is no equal for SizeOf, and a few other things. I am using Lame 3.98.2.exe in my app along with LameShell that works fine for resampling, but , not for decoding an mp3 to wav or encoding a wav to mp3. You can find the LameShell project at [URL] . LameShell is a wrapper for the Lame.exe file. Here is the complete LameShell class file along with my app button clicks for the following,
I am trying to extend an application to to write the details from textboxes on a invoice form to an xml file.I have created 3 methods for my invoice class which will open the invoice xml document, write to it, and close it.The open Invoice method creates and invoice.xml file and writes a start tag named invoices.
The WriteInvoice method writes an invoice element for the invoice with attribute named customerName and three child elements named ordertotal, discounTotal and Invoice total. These values are taken from the textboxes form the form.
The CloseInvoice writes the end tag for the root element(invoices) and closes the file.
I have wriiten code for these methods but can only get the open invoice method to work.
My code for the 3 methods is shown below:
Public Sub OpenInvoices() Dim sInvPath As String = "C:MurachBeginning VB.NETExercise startsVB.NETChapter 14InvoiceInvoices.xml" Dim InvoiceWriter As New XmlTextWriter(sInvPath, Nothing) InvoiceWriter.Formatting = Formatting.Indented 'Set formatting of XML file
I have managed to read a sheet from a excel workbook and pop it into a datatable.
Public Function GetSheet(ByVal SheetName As String) As DataTable Try MyDataTable.Clear()
[Code]....
My understanding is that if I make changes in the datagridview it is reflected in the datatable.
So now I want to write the updated datatable back to the appropriate worksheet.
I have read about "insert into" or "update" etc but it is very specific columns and rows.
One other thing, when I set the datagridview datasource as the datatable I get about 9 other columns such as TABLE_SCHEMA TABLE_TYPE etc. Any pointers wher thay are coming from and maybe how to get rid ofthem?
