In C#, Why Does A Datatable Not Know The Type Collection Of Rows
Jul 8, 2010
I have recently started .NET programming, and looked at both VB.NET and C#. In VB.NET, a strongly typed Datatable cosisted of a collection of strongly types rows. Therefore, for example, this statement would work:
lCustomerTable As CustomerDataSet.CustomerTable
lCustomerRow as CustomerDataSet.CustomerTable.CustomerRow
lCustomerTable = TableAdapter.GetData
lCustomerRow = lCustomerTable.Rows(0)
However in C#, it seems i have to explicitly cast the returned Row to a CustomerRow:
lCustomerRow = (CustomerDataSet.CustomerTable.CustomerRow)lCustomerTable.Rows[0]
Should the dataset not create the object type definitions when creating the table adapters and SQL dataTables?
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Jul 12, 2011
I'm trying to query a DataTable to get a collection of rows but I'm finding that my search string has to be the exact length of the columns width. So, for example this won't work:
Dim rows As DataRow() = (From r In myTable.AsEnumerable() Where r.Field(Of String)("fname") = "Bob").ToArray()
...but this will:
Dim rows As DataRow() = (From r In myTable.AsEnumerable() Where r.Field(Of String)("fname") = "Bob ").ToArray()
The search term ("Bob") has to be padded with spaces to make it equal in length to the column width (10 characters). Is this how it's supposed to work or am I doing something wrong?Also, how can I do a LIKE search? So for example, I want to search for all names that start with "Bo" or whatever. ie. "Bo*".
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Jun 6, 2011
I'm am creating a "pop-up" CheckedListBox over a button on my DataGridView. The values in the list are going to be filtered based on the value in column 0 of the DataGridView.I have already pulled in a "master" DataTable with two columns: ACODE and MATRIX.I want to call the following function and return an array of strings that I can use to build this CheckedListBox with. The line between "For Each r" and "Next" generates a "Number of indices is less than the number of dimensions of the indexed array". The number of items is variable in the array so I can't predefined it. I know I'm going down the wrong path.
Function StudyGroupSamples(ByVal sampleType As String) As String()
Dim thisArray() As String
Dim theseRows() As DataRow
[code]....
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Aug 4, 2010
this is more a theoretical question i asked myself.I remembered that BinarySearch of an ordered List(Collection in general) is faster than finding Rows with Datatable.Rows.Find or DataTable.FindByPK with a primary key value.Hence i fill a Datatable from Database in a shared constructor and immediately after that a List(of Int32) that contains all primary keys from that table. Later i will check with BinarySearch if the List contains primary-key values. But because the datatable contains only the PK-Column anyway, i asked myself if there is a way to avoid the huge overhead of filling a Datatable and after that adding all Rows to a List. Is it possible to fill a generic List(or other collection-type) instead of a Datatable/Dataset directly from a Dataadapter?Maybe i'm off the track and there is another way to avoid the Extra-Loop that i'm missing.
The code of filling the DataTable in a strong typed Dataset and the List:
Private Shared w205CorrectSWUpgrades As New List(Of Int32)
Shared Sub New()
[code].....
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Sep 2, 2010
how to add Rows programmatically to the DataGridView's rows collection when the control is data-bound? here is my code but i got error as "Rows cannot be programmatically added to the DataGridView's rows collection when the control is data-bound? "
[Code]...
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May 8, 2012
I have three sub tables that I want to process. For each I want to combine the rows, as they are only different by contents in the second column(I want to do the same to the fourth column, later):
'Sub table 1
xx|C201 |02300877 |Samsung |....
xx|C201 |02300877 |Toshiba |....
xx|C213 |02300877 |Samsung
[code]....
p.s. For the fourth column, Manufacturer information , I want to do the same and I'd probably get something like this for the final table:
xx| C201,C213,C606,C619 |02300877 | Samsung
xx| C201,C213,C606,C619 |02300877 | Toshiba
xx| C303, C305,C712 |02301163
xx| C207, C209, C708 |02301165
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Sep 1, 2011
Can anyone tell me why "Rows cannot be programmatically added to the DataGridView's rows collection when the control is data-bound." I keep getting an error "Invalid Operation Exception was Unhandled" error. All I am attempting to do is allow the user to select products from a list(or a second datagridview) and have it added to the datagridview so they do not have to type in every cell since the other cells are not visible because they do not purtain to their needs. Plus they will be able to save all items at the same time.
[Code]...
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Sep 13, 2011
I have two datagridview's both are databound. First one shows items for sale and the second stores all the items that were sold. I am trying too transfer selected rows from one to the other but no matter what I keep getting told "Rows cannot be programmatically added to the DataGridView's rows collection when the control is data-bound."
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Apr 14, 2012
Dim _tableBackLogs As System.Data.DataTable
Do While i - 2 > 0
_tableBackLogs = Global.DataAccess.GetDataTable("SELECT SubjectID,SubjectName,Grade FROM SubjectPI WHERE RegNo='" & CInt(HttpContext.Current.Session("userName")) & "' AND Status='Fail' AND Semester='" & i - 2 & "'")
i = i - 2
Doing this replaces the previous data in the DataTable. I want to retain the previous data i.e i want the new rows to be added to the DataTable w/o replacing the previous rows.
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Apr 22, 2010
I am writing a program that needs to read a set of records that describe the register map of a device I need to communicate with. Each record will have a handfull of fields that describe the properties of each register. I don't really need to edit or modify the data in my VB or C# program, though I would like to be able to display the data on a grid. I would like to store the data in a CSV file, or perhaps an XML file. I need to enable users to edit the data off-line, preferably in excel.
I am considering using a DataTable or a Collection of "Register" objects (which I would define). I prototyped a DataTable, and found I can read/write XML easily using the built in methods and I can easily bind to a DataGridView. I was not able to find a way to retreive info on a single register without using a query that returns a collection of rows, even though I defined a unique primaty key column. The syntax to get a value from a column is also complex, though I could be missing something on both counts.
[Code]....
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Apr 1, 2009
how to loop through DGV selected rows collection?
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Jun 8, 2009
I would like to create a group/collection/set of unfinished rows that I can later add to a datatable.I have tried to do this by creating a DataRowCollection, and then create a new row based on the table I want then add it to the collection. Doing that I get a NullReferenceException though.Using the new keyword for dr does not work.[code]......
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Aug 9, 2011
i encounter this error while passing a string as datatable.
I populate combobox1 with tables/sheets from excel and each table has datarows which i want to get the data and import to sql corresponding table, so, I declare
Dim XLSTableName as String = Combobox1.SelectedItem
And I encounter the this error : Conversion from type 'DataTable' to type 'String' is not valid
how do i return the combobox1.SelectedItem as Datatable cos if i declare
Dim XLSTableName as DataTable and pass it to the select Command thus:
Dim objCmdSelect As New OleDbCommand("SELECT * FROM [" & XLSTableName & "], ODBConn)
to obtain the dataRows I got the following error: operator '&' is not defined for types 'String' and System.Data.DataTable'
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Oct 1, 2011
devicetypecollection = New Collection
devicetypecollection.Clear()
For Each dr1 As DataRow In _Default.ide.dtds.Tables(0).Rows
[code].....
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Jan 6, 2011
Is it possible to query an unbound DGV to get a collection of rows where a column contains a certain value? Can LINQ do this?
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May 29, 2009
I have a DGV that has a datasource to load the rows I need for display.
Now, I need to save the selected rows to a DataTable.
binding the DGV. I created the DataTable in my DataSet dsProfiles1 and created a BindingSource - bsDataTableDGV
DataTable:
ClientID Int32 not null PK
ClientName String not null
ProgramNo Int32 Not Null
[Code].....
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Feb 15, 2012
I have a form with a textbox and a add button. User can write a name down on the textbox and click add button. it will save in a datatable with auto ID. After that, the textbox is cleared and the user can write another name on the text box and click the button. This should add to the existing datatable on memory with existing ID + 1. Show on the gridview. (this is just for display purpose to confirm it works)
I have a datatable like this.
Button1.click() event
Dim name = txtname.Text
Dim dt As New DataTable
dt.Columns.Add("ID", GetType(Integer))
[Code] .....
At the moment I have sometime like the code above. in the real program, it is not just name and it is not just one datatable so i just mock up some code. And this code for aspx.
<asp:TextBox ID="txtname" runat="server">
</asp:TextBox><asp:Button ID="Button1" runat="server" Text="Button" />
<asp:GridView ID="GridView1" runat="server">
</asp:GridView>
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Dec 16, 2011
I am trying to make it so when I use Me.Controls("Timer1") for example I can access specific commands for a timer such as Stop() Start(), I tried CType() and typed in "Timer" as the type but it says the control type can't be converted to the "Timer" type.
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Oct 6, 2009
Datatable object within class function + garbage collection?
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Nov 4, 2011
The tables described herein both utilize composite keys. I have a parent table that stores eligibility information per "case". The child table stores eligibility information regarding each individual associated with the case. The child records are differentiated by pin number to make them unique in the child table only.
I am using NHibernate v3.1 with Fluent NHibernate v1.2, both acquired via NuGet packages. The entities are mapped in using the Fluent NHibernate auto-mapper functionality. Any custom mapping is done in the mapping override method for each entity.
Another thing to know is that these tables do not have a "primary key" defined in DB2. They only have "unique keys", which are what you see in the composite key definition below (see code).
T0026_AG_ELIG is the name of the parent table and the corresponding POCO class.
T0265_AG_IN_ELIG is the name of the child table and the corresponding POCO class.
Problem:
The problem is that when I execute the query, all the data is queried, the parent record is successfully mapped to the class, but the returned child rows do not map into the collection on the parent class. NHibernate does generate the queries for the parent and child data. When I execute my own query against the database, the correct data for the conditions does come back. For some reason, the child records are just not being bound to the property on the parent (T0026) class.
Question:
What do I need to do to get the multiple rows coming back from T0265_AG_IN_ELIG to map to their corresponding class and load properly into the specified collection property on the parent class (T0026_AG_ELIG)?
Collection Property of Parent (T0026_AG_ELIG):
Public Overridable Property IndividualEligibilityRecords As IList(Of T0265_AG_IN_ELIG)
Mapping Override for Parent (T0026_AG_ELIG):
mapping.CompositeId() _
[Code].....
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May 2, 2009
Here is my code.....This code works fine but when I click on add button (Which is used to update record) the following exception/error comes
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Oct 18, 2011
I'm still pretty new at .Net and database coding, and am working on a small program that is generating an error and I'm not sure how to resolve it.[code]The following statement is giving me the error below: m_DA.Update(m_DataTable)"Update requires a valid InsertCommand when passed DataRow collection with new Rows".I know the answer is going to be very simple, but I'm at a loss. I would greatly appreciate it if someone could point out the flaw in my code and how to correct it. And yes, I have done fairly extensive searching on this error, but none of them give any idea how to fix it, they just hint around at what's wrong.
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Jan 14, 2011
I Have a datatable in .net. I need to flip the location of two of them. For example, a datatable that the select statement had an order by priority clause. The user wants to up the priority of a single row by selecting it and clicking increase priority, how do i move a row up (AKA flip two rows)
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Jul 13, 2010
I have this sub :
Private Sub error_out(ByVal line As Integer, ByVal err_col As Integer, ByVal err_msg As String)
Dim ln = t_erori.Rows.Add
[Code]....
I suspect this is because it's trying to add the same row twice.
How can i make this work ? Or what else method could I use to do this ?
I need this datatable because my app is writing some results in there, but any other method to store the results that works with parallel.for would be ok.
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May 13, 2012
I have one datatable tempDT with value :
[Code]...
The problem is I want merge duplicate serial_no into one row which the value of testong adding to new column. I have tried many ways, but I can't find the solution. Here is my code behind :
[Code]...
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Apr 17, 2009
I have a datatable object, which is populated from a webservice.Apparently, the web service just throws everything (data) back to me. The data which gets in my datatable looks like this:
Dept Code Value
Science ABC 5
Science ABC 6
[code].....
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Apr 8, 2010
At the moment I use this code but I have 591 rows to delete and it takes forever to loop and delete each row on an individual basis
[Code]...
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Feb 10, 2012
i need to delete some rows from datatable
i don't know the indexes i have 2 columns to idendify the rows to delete
how to achive this in easy way
i don't want to delete inside loop wat will happen if i have 2 million rows? tats why i don't want to delete indendify the rows and delete in loop
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Mar 20, 2009
I have a Datatable in my code in vb.net. I need to delete rows from the datatable. The name of my Datatable is "temptable".in my row deleting event of a Gridview control. I wrote code as follows:
In the Row_Deleting event of Gridview:
temptable.Rows.Remove(Gridview1.Datakeys(e.RowIndex).value)
But,it shows an error as follows:
"Cannot cast System.Int32 to System.Data.Datarow".
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Jan 9, 2009
IDE : VS 2008,Platform : .NET 3.5,Here is my DataTable columns :ID Note DetailI want to write sth like this :
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