VS 2008 - How To Get Unique Values From Specified Column Of DataTable
Jun 16, 2009
I'm trying to make a method that can get unique values from a specified column of a DataTable. The problem is that the column may be string, integer, etc. I'm not sure what type of variable the (Of T) is.
Private Sub GetColumnUnique(ByVal dbTable As DataTable, ByVal ColumnNumber As Integer, ByVal ColumnType As ???)
Dim results As List(ColumnType) = (From item In dbTable.AsEnumerable Select item.Field(ColumnType)(ColumnNumber)).Distinct.ToList
End Sub
How can I query a DataTable to find all of the unique values in a column? SQL has the 'unique' or 'distinct' keywords, but I dont know how to do this against a DataTable.
I'm using an Infragistics UltraWinGrid with a column of drop-down boxes. I don't want the user to be able to select the same value for multiple rows in that column. Is there a simple (or heck, I'd settle for advanced) way to do this? I'm using VB.NET
-EDIT-
I tried setting a filter on the data source for the drop-down box. But when I did that, the values in the other boxes in that column started disappearing (not the values themselves, but the descriptions that they were supposed to represent, so instead of reading "Information", it just said "1"). All of the cells in a column refer to the same combo box, so if you filter out a value from the data source for one of them, you filter it out for all of them. I'm currently trying to catch a CellChange event and check against all other currently-used values. If it was already used, I would put up a message saying as much and revert back to the old value. However, the value comes back as the previously-saved one, so... not helpful. About to see if I can use the "text" property.
I want to loop through a databale and change the values of a specific column in that datatable.eg: the database returns Request_ID, Desc, Date and Status_Ind. The Status_Ind column contains integer values. I dont want to show the integer values to the user. I want to convert that to a string value based on the integer values returned in that columns.
I have a DataTable that has several hundred rows.I want to get a row count of distinct values in a particular column.For example, I have a DataTable of Product Orders, but I want to get the number of unique Customers.
I was using this code, but I can't rely on it because my binding source is filtered from time to time.If my binding source has filtered out all rows datatable.DefaultView returns 0 rows.
Alright, I have this Access Database. It has 6 Columns: ID | Class Name | Class Code | Class Room | Grade | Teacher
My ID is the Unique Column that I need to reference back too when Updating my other Fields so I get the correct field.How do I do this? Properly.I've been thinking of a method but I doubt it would work.First I would start off selecting all the ID's and then LOOP through all of them, and then rewrite them to to + 1 Each time I make a Delete, so Each Time it will be a consistent 1 2 3 4 5 6 7 8 9 10 .... etc... Then I can reference from that to my Combo Box Selected Index + 1 to get the Correct Row which corresponds with the Selected Item.Will this work? Or will I still need a Unique Fields that I reference back too.
I am trying to populat a treeview with nodes that are the values of a column in a datatable. I have managed to get the correct number of nodes but the text is not displayed next to the nodes, there is just a 3 shape but the other way round and with square corners shown.
The code is below. I would like to have these parent nodes populated on the form load and then (i think this is what i have read) to be quicker i would like to then load the childnodes once a parent node has been selected, as i don't want to load the whole database on form load or when the form is refreshed.
I have this Access Database. It has 6 Columns: ID | Class Name | Class Code | Class Room | Grade | Teacher My ID is the Unique Column that I need to reference back too when Updating my other Fields so I get the correct field. How do I do this? Properly.
I've been thinking of a method but I doubt it would work. First I would start off selecting all the ID's and then LOOP through all of them, and then rewrite them to to + 1 Each time I make a Delete, so Each Time it will be a consistent 1 2 3 4 5 6 7 8 9 10 .... etc... Then I can reference from that to my Combo Box Selected Index + 1 to get the Correct Row which corresponds with the Selected Item.
Unique constraint - these columns currently doesn't have unique values..?? I have created Unique Constraint with 3 columns. My code works perfectly but once - two users @ same time entered same data and somehow it saved in DB; after that incident. This UniqueConstraint gives me error - These columns currently doesn't have unique values. How can I check if user enters this kind of entry or how can I restrict the Entry?
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
I have following codes str2 = "select sno,name from employees where sno =" & Val(Me.TextBox1.Text) cmd2 = New SqlClient.SqlCommand(str2, con) da2 = New SqlClient.SqlDataAdapter(cmd2) dt2 = New DataTable da2.Fill(dt2) Now dt2 has two columns as sno and name But I want to add a 3rd column city type char(80)
I have a DataTable with multiple columns including AccountNumber, Year, and Month. I am exporting the information in this table to an Excel workbook. Since this table has the potential to be extremely large, I must check the number of records in the table (since Excel can only have 65536 rows or something like that. If the original table is small enough, I need to put all of the records in a single worksheet. If there are too many records for one worksheet, I need to separate the records into multiple worksheets based on AccountNumber. Additionally, if there are too many records for a specific AccountNumber then I need to split that AccountNumber into multiple worksheets based on Year.ng:
Worksheet Name ---- Number of Records 1111 ---- 150,000 2222 ---- 50,000
I have a datatable and I want to create a text file using this datatable. I want that each row of the newly created text file is unique. If there is a duplicate row, then it should add * to both rows ( duplicate rows)
I am using following code:
Dim str As String For Each row As DataRow In dataTable.Rows str += row(1) ' This is text data
I have a DataTable which I want to check if values in three of the columns are unique. If not, the last column should be filled with the line number of the first appearance of the value-combination.
[Code]...
I solved this by iterating the DataTable with two nested for loops and comparing the values. While this works fine for a small amount of data, it gets pretty slow when the DataTable contains a lot of rows.My question is: What is the best/fastest solution for this problem, regarding that the amount of data can vary between let's say 100 and 20000 rows? Is there a way to do this using LINQ? (I'm not too familiar with it, but I want to learn!)
I am working in vb2008.TableAdapterManagers are a new feature in vs 2008 and I would like to understand how to use them properly.I have about 30 tables in my database that are unique to themselves and donot link to other tables.I have created a dataset.xsd in my solution and dragged in my database tables of interest.A unique datatableadapter has been identified in the dataset1.xsd for each datatable.Rather than using the identified datatableadapter for each datatable operation, should I be using the dataadaptermanager for each unique table?
am trying to calculate the values in rows in column 6 based on values of column 5. Bellow is the the code I am using I get a run time error about the string not formatted properly
I am trying to add the returned values from an array to the rows in a data table: Here is my current code the values load properly into the list box but not the table, each row ends up with the same value.
current code not working correctly Dim dtrow As DataRow Dim lat As Double = CDbl(34.213209)
For each loop through a DataSet, I need to store the values of 2 columns (we'll call them ColumnA and ColumnB) so that I can use them to search the same DataSet again later.The DataSet stores the results of a search and places the value of ColumnA into a ListBox as a new item.When the user clicks on this ListBox item, the application will loop through the DataSet again using the value of ColumnA and the value of ColumnB as criteria to identify the correct row in the DataSet to return.This would be a lot simpler if the value for ColumnA was unique every time, but a value will inevitably be repeated on occasion. That's where ColumnB comes in. This column's value is likely to be unique 90% of the time, and, given the nature of the information in the DataSet, if either column duplicates, the other won't.So I've thought of adding the values for ColumnA and ColumnB into a 2 dimensional dynamic array, but I'm doing something wrong apparently.[code]
currently, what i want to do is, add a column in a table "default" during runtime. Well, I've got that covered already.
The problem is, the column names are actually taken from the users input through a textbox or drop down list and of course, if the same column is added already in the table, it generates an error since it has to be unique.
That is why i wonder if it is possible to know if a column already exists without viewing the form which contains the grid view of that table?
