C# - Added Overhead To Looking Up A Column In A DataTable By Name Rather Than By Index?
Apr 13, 2010
In a DataTable object, is there added overhead to looking up a column value by name thisRow("ColumnA") rather than by the column index thisRow(0)? In which scenarios might this be an issue. I work on a team that has lots of experience writing VB6 code and I noticed that didn't do column lookups by name for DataTable objects or data grids. Even in .NET code, we use a set of integer constants to reference column names in these types of objects. I asked our team lead why this was so, and he mentioned that in VB6, there was a lot of overhead in looking up data by column name rather than by index. Is this still true for .NET?
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Feb 21, 2011
I am creating a datatable and then adding a column to it which is filled with data from existing column and parsed into correct format DateSold is my existing column from my datafile and I create NewDateSold by adding the column to the existing table and then parsing the information in date format.
This is added to a binding source which then is used to populate a combobox I want to be able to sort the combo box by NewDateSold Desc I was able to this on the original column by simply using the "order By" in my query, it seems now that I added new column it is no longer sorted? I am finding different solution such as using dataview and wish to know the best way to do this
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Mar 23, 2012
I need to sort a datatable. I do it with linq this an example
Dim query = From c In dt.AsEnumerable _
Order By c.Field(Of DateTime?)("LastPurchaseDate"), _
c.Field(Of String)("LastName") Descending
Dim dv As DataView = query.AsDataView
But my problem is that i need to sort the fields not by passing the name of the column but the index of that.
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May 16, 2012
i have two datragridviewcomboboxcolumn,and two textbox column in a datagridview.each combobox column is binded to separate binding source.
column names are sl_no,col_empname,col_empworktype,Col_Hours etc.and
displaymember,datapropertyname,valuemember and for comboxcolumn are
col_empname:-emp_name,emp_id,emp_id
col_empworktype:-worktypename,worktypeid,worktypeid
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Aug 6, 2010
I am trying to add NewRow to the database by using datatable in dataset, but before I do that I want to make sure that row is not already there. I create new row for the datatable I am working with, fill it with information. I fill datatable with the row from database that has the same primary key as my NewRow by using tableadapter.fill method, but when I do that my NewRow that was never added to the datatable is filled with information from database(and not information that I assigned to it). I count rows in my datatable before I fill it and it's 0, so why is my NewRow affected by Fill command? (I am using VB.NET 2005 Framework 2.0)
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Apr 23, 2012
i am having trouble putting a value in a textbox. Each time a ticket is sold i put the total price in a textbox, each time a ticket is sold for the same concert it increases by adding its self to the total price. It works at the first sale, but after that it breaks down. here is the code
Private Function DisplayMoneyTaken() As Integer
Dim totalMoney As Integer
'open the database connection
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Oct 6, 2011
I have a datatable property called prpParametersTable in a class called clsBatch. I have a procedure that sets a datatable variable called dtP equal to prpParametersTable at the beginning of the procedure. I then add three new columns to dtP.Here is my problem. When I add the three new columns to dtP my original table prpParametersTable also gets those columns added to it, why? I only want to add the three columns to dtP and not prpParametersTable. How can I do that?
Private Function prvfnc_InsertBatchParameters(ByRef cnn As SqlConnection, ByRef trans As SqlTransaction) As String
' set new columns that have BatchID, Insert DateTime, and UserID for the SQLBulkCopy method below
Dim clm As DataColumn
Dim dtP As DataTable = clsBatch.prpParametersTable
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Mar 15, 2009
I have a datatable which has 5 column. It is possible to copy only its 2 column in and save it into new datatable.I used this code but it copies all the 5 column
Code:
Dim qry As DataTable = (From obj In temptable Where obj.Item("Column1") = 0 _
Select obj).CopyToDataTable
i used this one but it is not supported
Code:
Dim qry As DataTable = (From obj In temptable Where obj.Item("Column1") = 0 _
Select obj.item("Column1"), obj.item("Column2")).CopyToDataTable
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Apr 25, 2010
I'm trying to create a datagridviewrow and add data to it at runtime. I want the row to have the cells correspond to the columns in a datagridview, so that when I add data to the cells i can call the column name (the columns are likely to change around, so i think the name is better to use then the index).I create the row using the following code:
Dim row As New DataGridViewRow
row.CreateCells(Datagrid)
and the column using the following code:
Dim col As New DataGridViewComboBoxColumn
col.HeaderText = "Reference"
col.Name = "Reference"
datagrid.Columns.Insert(0, col)
I would like to add data to the row via the following code (or something similar that uses the column name instead of the index:
arow.Cells("Reference").Value = Detail.Reference
However at runtime I get the exception Column named Reference cannot be found. Parameter name: columnName I have a sneaking suspicion that the cells cannot be accessed with the column name because the row isnt really attached to columns yet (the row hasnt been added to the datagridview yet. (I tried cloning the cells of a row and then adding them to the row but no success)?
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Apr 6, 2010
How can i get the Column Index and the Row Index when I click on the ListView?The ListView1.FocusedItem.GetSubItemAt(e.X, e.Y).Text function only gets the text of the first column, I can't find the option of getting the Index of the Column and Row upon clicking.
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Jan 18, 2012
Is there a way to find the column index of a datagridview column using the columns DataPropertyName?I currently use a loop (shown below in the class) which is kind of ugly, but it works. I'd like to do something like this, which seems more elegant.My goal is this, I store the users DataGridView column settings (i.e. DisplayIndex, Visible, & Width).When the user opens the form that contains the datagridview I want to get those settings from the database and apply the settings to the datagridview.[code]
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Apr 20, 2012
I have a Datatable where i added data from textbox when i want to edit selected datatable rows from gridview to eidit these values will be showing in their respected fields but when i click update button the only first row in gridview will be updated either i select first row or any other row in gridview for editing whereas i want to update the selected rows data. NOTE: I was design datatable visually under vb.net 2008 designer and the datatable have not any primarykey i am using following code under btnupdate event
Dim i As Integer
StoreDBDataSet.Tables("DataTable1").Rows(i).Item("Code") = txtCode.Text
StoreDBDataSet.Tables("DataTable1").Rows(i).Item("Description") = txtDescription.Text
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Feb 25, 2010
I have set up a class as a facade to access the session variables for my app. In this app I store an entire dataset for a particular employer as a session variable.Within one of the sub pages I have a button that adds a row to an existing table stored in that dataset.
Dim curRow As Data.DataRow = mySession.tWorksiteOtherMeasures.NewRow()
curRow("lngWorksiteID") = getSelectedWorksiteID(getSelectedSiteID())
curRow("strMeasure") = ""
curRow("lngStatusID") = -1
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When in the code to add the row the row count increments and the row exists. Once out of that scope the page refreshes due to the button being contained in an updatePanel. When that happens and I click the add button again the row counts for that item reset to 0 and 1 after the code runs. The previous added row is gone.Here is how the Dataset is assigned from the web service:
Public Shared Sub loadDSEmployer(ByVal strUserId As String)
Dim myService As New someservice.service
mySession.dsEmployer = myService.GetEmployerAndSites(strUserId, isInternal)
End Sub
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Feb 6, 2012
Is it possible to get the row index of a DataTable so that you can access the previous and next row? For example I have a DataTable that contains two columns ChapterTitle and PageURL. This is for a table of contents of a book. ChapterTitle is the chapter name and PageURL is an HTML page that contains the chapter (chaptername.html). When going into one chapter of the book I want to be able to tell which is the next and previous chapter.
After finding the chapter that I'm currently in how can get the next and previous rows?
ChapterTable.Select("PageURL = '" & PageURL& "'")
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Apr 11, 2010
How can i get the index of an element in datatable which i got using the select method of datatable as
dim d as new datatable= 'some data source'
dim dr() as datarow
dr=dt.select("some condition")
now i want to find the index of first or second item which i have retrieved in data row. i mean there index in data table with out use of loops as loops take a lot of time when there is huge data in data table.
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Sep 12, 2011
I am wanting to update a datatable which is been created dynamically. Each row has a unique Id column. How can I retreive the row and update a column in it using the Id column
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Mar 6, 2009
I am working on a program to match overlapping images together to make one complete image. This isn't for panoramic purposes, it is from a video game generated overhead map, so there is no perspective issues to deal with and the overlapping images (gained from screenshots while a player moves) should be pixel perfect (still running tests to verify this, but lets assume they are pixel perfect at this time).
1) I need to compare each new (small) overhead map section to the larger map, find what edge it fits on, and copy it over.On other forums I have seen people suggest taking the bitmap apart in the form of an array of colors, or 3 arrays per image for r, g, and b. I am wondering why this is done instead of directly going to the bitmap object and using GetPixel. Is an Array lookup significantly faster? Speed would be an issue with my program, I would like to do this match as fast as possible, and the overall map could become large, even if I keep making new map sections to manually paste together later.So, faster to loop through a graphic with getpixel, or faster to go through 3 two-dimensional arrays with r, g, and b, or faster to go through 1 three-dimensional array with rgb all inside it?
2) The bitmap object that contains the overall map will keep getting larger. What is the best way to resize that bitmap dynamically?I am thinking of just making a new, larger bitmap when I get near an edge, then using getpixel and setpixel to copy over the old bitmap to the new one. Is there a faster way to make a new, larger bitmap object containing the old one with the graphics class? I admit to finding the graphics class somewhat confusing in how methods on it affect the image object that is defined as it's surface...or something. There might be a faster way with graphics and drawimage, but is that really faster than a getpixel/setpixel loop? Finally, if I do store the graphics data in arrays instead of actual bitmap objects, would redimming the array be the best way? If I need more room at the 'beginning' of the array I would have to make a new array and then copy the data over shifted. And this might involve 3 arrays if it is best to use one each for r, g, b.
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Feb 21, 2012
I know this is old hat, but when you're faced with a problem you cannot solve yourself, you need to find someone with the correct answer.In short, go to the wise.
I am working on an application that has a lot of records, and it uses a listbox control bound to a binding source attached to a table in a data source.A new record with data is added to the binding source's attached table, and, of course, to the underlying sqlServer database table:
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Apr 29, 2011
I have a data set in the User control . It was working fine but now when I started using another copy of the user control it started showing error DataTable internal index is corrupted: '5'.
dim dv as dataview
dv = new dataview(ds.tables("Names")
dv.rowFilter ="CatNum ='"& val&"'" 'This will always give one row only
dv.item(0)("Names") = myvalue ' here the exception is occurring
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Mar 20, 2009
I understand that DataTable.Select() returns an array of rows. I just want to know whether these is a way to get the row indexes as well.
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May 7, 2006
I have a datatable with 10 records linked to a datagridview. When I initially load the datagridview, row 0 in the datagridview = row 0 in the datatable - based purely on the order they load, and the datatable's default sort order. I then filter my datagridview and am left with 5 records. Is there a way of determining programatically, the actual datatable row number of a row displayed in a datagridview, considering that row 0 in the datagridview is now not necessarily row 0 in the datatable?
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Dec 30, 2011
I have a question related with VB.Net Code. I see that the DataTable we can use: DataTable(0)'This return a DataRow with the selected index In the intellisense I see that this functionality can achieve with a extension... but, If I create a extension, always I need refer the Extension before to use it
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Sep 27, 2010
When i load my database i load it into a DataSet.When i search the database i load the results in to a DataTable.I want to find what index a search result has in the DataSet.When navigating the dataset i can use this code to get the index ds.Tables"Filmer").Rows.IndexOf(ds.Tables ("Filmer"). Rows(inc))But i can't make i get the dataset index of a search result from the DataTable.I thought that i could use the same code when navigating the DataTable, but it only returns.
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Sep 16, 2010
With this project, I created a SQL Server DB with related Dataset and DataTable a while ago with about 10 columnsWith the code below, I fill those columns with values in a new row and add to the datatableThe datatable is bound in a datagridview and all has worked fine until I tried to add a new column to the dataset/table. After adding the new column and rebinding the datagridview to the updated table, the DGV now shows the new column, but the data for that column fails to show up in the DGV.
Dim dt As Date = DateAndTime.Now
If My.Forms.DataGenerator.TextBox4.Text <> "" Then
My.Forms.DataGenerator.TextBox8.Text = dt
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Nov 30, 2010
Dim pctofpax As New DataColumn
pctofpax = New DataColumn("PCTPAX1", GetType(Decimal))
pctofpax.Expression = "[ASOFPAX] / [YEPAX]"
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Mar 17, 2011
I have a datagrid view in my vb.net application. I want to update this DataGrid View so it shows any changes to the database (More specifically when a Column is added). I have tried
DataGridView1.Update()
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Feb 5, 2012
I have a data table, i want to add a new column on that table, the data in that new column will depend in the data from another column. Now i can think of two ways to accomplish this, first is loop through the whole table and do the statements to get my new columns appropriate data. the second approach would be to give the new column an expression, then convert the table to xml (to remove the expression) then convert the xml string back to datatable.
Now, is there any other way around this? what could be the most optimized way in solving this task?
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Oct 22, 2010
I've looked around and can't seem to find a solution to my problem. I have an EventLog object which inherits DataGridView and has a public variable EventList which is a List(Of EventLogItem). EventLogItem has seven properties which describe the event, including Index which is set to EventList.Count each time an entry is added (so, it should be unique). Everything has worked just fine until I tried to add an entry from a serial port DataReceived event handler upon which I receive the following exception:An error occurred creating the form. See Exception.InnerException for details. The error is: An item with the same key has already been added.Clicking 'View Details' and expanding the InnerException yields no more information. Here is some relevant code:
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Apr 30, 2010
The dropdown box displays all the items previously added to that column.
I want the user to be able to enter a new value OR just pick a previous value from the dropdown list. (This is when inserting a new row)
Problem:
Whenever I enter a value, it jumps around in my table like its on acid or something. Whenever I select a value from the list, it takes me to the line in which the value was originally entered.
How do I get it to do what I want.
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Oct 27, 2011
After Filling a DataTable in GridView's DataSource . A column with check box Type appears but it created as read only column and I can't enable it or make it editable... even i tried .readonly = false and still can't be edited
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