I just discovered the DataTable.Select-function, and boy I'm glad I found it! It makes my code run several times faster. But, I don't quite understand why it's so much faster than my previous code. In my first code, I looped trough my DataTable to find the specific row, like this:
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I am trying to display value of the field ("UserID") for every row exists in datatable to checkboxlist(make the checkboxlist item selected).
I used for loop, but only the field value from last row of RoleUsers table is selected in the checkboxlist.
Here is my code
Private Sub DisplayRoleUser()
Dim conn As SqlConnection
Dim cmd As SqlCommand
[Code].....
I've been using VB for some time now, but I must admit I am a little confused. I started learning with 2002, then 2003, 2005 and now 2008. I think database coding must have been going through a kind of transition when I was trying to teach myself the basics. As a result, I am not entirely clear on a few things..
1) What's the difference between a DataTable and a DataSet. Why would I use one over the other?
2) Personally I dislike using DataAdapters etc and much prefer typing my connections in code so I can see what's what. When using the visual tools things are 'hidden' from view and it's not clear what's going on - do others find the same or is this just me being old fashioned?
3) Using my code-based approach (ie: creating SQL connection, using ExecuteNonQuery and a SQLDataReader to read the results into my application) - is this less efficient than the alternative methods?
4) Finally...LINQ. Is it any better and should I be using it as standard practice?
I was trying to write the following select stmt but i am getting an error that the parsename is not identified.
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The next step is I need to build a randomizer to randomly select a row and read the columns of that row into varibles.I have a working randomizer that can randomly pick a number between min and max values but what I don't know if how to select a row / How to find out how many rows are available and how to read the values into varibles.Am I right in declaring an Integer Varible then using:
AvailableRows = DDT.Rows.Count
Then use my Random Function to pick a number between 0 and AvailableRows
I need to use .Select and filtering year on a date field,how can this be done,the next code give me error : the expression contains undefined function call year() vb.net For Each wRwTmp As DataRow In wTblC.Select("year(start_date)=" + wYear.ToString)Next
View 11 RepliesHi. what is the difference of sleep function and pause function (using timer) between a loop.
View 12 RepliesI am getting array of selected datarows from a datatable.select.I use the commands below to get that array or datarows
Dim foundRows() As DataRow
strExpression =
Here is what I tried.I have looked at examples by MS but they all just write to the screen and I have no interest in that.
For Each rowWork In foundRows
dtWork.Rows.Add(rowWork)
Next[code]....
"LineOfBusiness = 'CPP'"
foundRows = modXchange.pdtWork.Select(strExpression)
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
Unable to select multiple column in datatable
Code:
Dim Activitydtb As DataTable = DirectCast(ViewState("TalentcharacterActivty"), DataTable)
grdviewactivity.DataSource = Activitydtb.Select("SELECT
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I have a select statement and it will go to a datatable object, I would like to do the following
textbox1.text=datatable(first field value)
textbox2.text=datatable(second field value)
textbox3.text=datatable(third field value)
[Code].....
What is the major difference between 'for each' and 'for' loops in .NET? Is there any performance gain while comparing these two? Which one gives a better performance/faster/memory management?
I have a dataset which includes some numbers, I want to calculate the sum of the difference in the numbers how do I do this? For example my dataset looks like this:
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I want to loop through all the controls on a "panel" and bind them to a datatable. I'm finding it hard to detect the "end of the panel" - as I also have group boxes and such on the panel. At first I was using the "parent" control - but that doesn't work with group boxes.
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In VB6, Something.SetFocus sets the focus to that Something. No problems there - in .Net it's called .Focus.On another thread I was told (twice!) to use Something.Select in a particular scenario (which works fine by the way).
View 4 RepliesSomeone had coded a project in Java. THis was just a calculation that looped through 1000 iterations. We had done the same thing in Vb.net.Does anyone know the speed difference between Java and Vb.net for a long calculation loop? I had heard Java was very slow.
View 4 RepliesI have a database table that holds order information and saves the current gold price (world price) automatically at the time of entryif i look back on the table, and the saved gold price has a difference of the current gold price of + 100 i want to show that in a report
View 1 RepliesJust curious is there a "next row" method when looping through a datatable? Basically, I want to be able to go to the next row without having to go to the end of the loop. See my coded example:
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I am using a SQL query to fill a datatable from 2 associated tables. The first table has Products and the second has associated addonpackages. When I loop through my Products I am able to get all of the addonpackages for the first product but after that the datatable is only getting populated with the last addonpackage for each product. ie:
product 1 - all 6 packages are added tp the datatable
product 2 - only package 6 is added to the datatable
product 3 - only package 6 is added to the datatable
...and so on
My query follows. Why I am getting all of the info for the first product but just the last item for all others. No matter which product I would query first, I get all of the associated data with it but only the last for all others.
SELECT Products.ProductNumber, Products.Name, Products.Mnemonic, AddOnPackages.PackageNumber,
AddOnPackages.Name AS PackName, AddOnPackages.Mnemonic AS PackMnem
FROM AddOnPackages RIGHT OUTER JOIN
Products ON AddOnPackages.ProductNumber = Products.ProductNumber
WHERE (Products.Name = @ProdName)
ORDER BY Products.ProductNumber, AddOnPackages.PackageNumber
IDE : VS 2008,Platform : .NET 3.5,Here is my DataTable columns :ID Note DetailI want to write sth like this :
View 8 RepliesI'm trying to set the same value for all rows for a single column in a datatable without using for loop. Any faster methods to achieve the same.
View 2 RepliesI thought this would be simple but obviously not!
Basically, I have a date and want to do a 'between' on two date columns like this:
myDataTable.Select(myDate & " between (StartDate and EndDate)")
Where StartDate and EndDate are date columns that do exist in the DataTable.
I want to loop through my datatable column called SDESCR and created a string that looks like this.
Dim labels As String() = {"North", "South", "East", "West", "Up", "Down"}
this is what i am trying and it is not working
Dim labels As String()
For Each row As DataRow In tablegraph.Rows
labels = labels " ' " + row.Item("SDESCR") + " ',"
Next row
i want to read table row by row i have table with two columns but i want to read the first column only row by row her's my code
Dim col As String = "SELECT users.user1,users.valueid FROM users"
Dim cmd As New OleDbDataAdapter(col, CON)
Dim ds As New DataSet
[Code].....
I have an Access Database "WPS" with a datasheet "CompartmentDescription" having "CompartmentName" as one of the columns. I want to use each element of the column. How do we retrieve the data Using "For Each" loop.
View 1 RepliesI have created a gridview to allow users to type two fields in each row after that I added the user data into a DataTable now I want to insert this DataTable content into the database where each row will have 1 uniqe Id in the database without using loop.If it is not possible without a loop please show me how to do this with the loop Again I already have the DataTable filled up and it is ready to be inserted into the database?
View 2 RepliesI am trying to loop through a datatable, that will pass information to my stored procedure but it isn't working.even though it works when i manuelly
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim dv As New DataView
[code]......
Here is my DataTable columns :
ID Note Detail
I want to write sth like this :
//below code block is not the right syntaxFor each q in dtDataTable.Column("Detail)
strDetail = Row of Column Detail
Next
I am little bit stuck here .. I have a datatable as _
Dim dtPupil As New DataTable
dtPupil.Columns.Add("PupilId", GetType(Integer))
dtPupil.Columns.Add("Forename", GetType(String))
dtPupil.Columns.Add("Surname", GetType(String))
I made a select (assuming names combination will be unique)
Dim strQuery As String = "Forename ='" & forename & "' and Surname = '" & surname & "'"
Dim dr As DataRow()
dr = dTablePupil.Select(strQuery)
I wanna have PupilId as an Integer of the row that match, so
Dim PupilID As Integer = ??????????
What do I need to write here ? There will only be 1 row returned.
I have a datatable and I would like to get the MAX number from this table where Term Number (first Column) is a certain value. If my datatable is declared as dtMyTable, I'm assuming I need to use dtMyTable.Select(), but I'm not sure if this is the best way.
View 2 RepliesI'm trying to get value from Datatable after Select Method.Select Method should return only one record.
Dim y As DataTable = CType(HttpContext.Current.Session("tb"), DataTable)
Dim products = y.[Select]("StnID" = "'" + stnID + "'")
Dim size = DirectCast(Products(0)("Shape"), String)
if I replace products with y--(DirectCast(y.Rows(0)("Shape"), String), it works.(which is before Select method, so it's useless) products is datarow object and I can't seem to get the value same way as datatable.How do I get value from datarows?