I want to set each element of collection in one row, but they are always added in one column, not row.
var headers = new List<string> {...};
var row = 4;
worksheet.Cells[row, 2, row, headers.Count()].LoadFromCollection(headers);
From code - I select Range in what I want to load collection. But it doesn't work as expected. Result in image (Dates should be in row as column headers).
Using EPPlus version 4.5.3.2
LoadFromCollection is supposed to work like that. Normally you pass it a collection of a complex type, then the properties of that type become the column headers, while each item in the collection is populated on a separate row.
Since you're passing a simple type, it's just like you passed a complex type with a single property. Every value goes on a different row.
If you instead want the items in your collection to be on the same row, just write a for loop to iterate over the items in the collection and add them.
I have a series of lists and classes that implement a table of data. The basic classes are: Columns, Rows, and Cells. The Rows contains some ID information and list of Cells which contains the row's value for each column. Currently I create the rows in a cell with code like this
void CreateRow()
{
Row newRow = new Row();
newRow.ID = idInfo;
foreach (var Column in Columns)
{
newRow.Cells.Add(new Cell(Column.ID));
}
Rows.Add(newRow);
}
The works fine, but in some cases am calling CreateRow() 20,000 times and have 200+ columns. So I am wondering if there is a more efficient way to populate the cells since the cells in a certain column in each row are identical.
Any ideas?
Thanks,
Jerry
Currently you create unique Cell object for each position in your matrix - that's a lot of cells given your use case of 20.000 + rows.
One approach to be more efficient could be to not add the cells at all when you construct the matrix, but only when you try to get or set its value (i.e using Lazy<T>).
Assuming you set the value of a cell before retrieving it, you could then have a factory method for creating a cell with a value - make the Cell object immutable and when you are "creating" a Cell for which you already have another cell with an identical value, return that cell instead. This could reduce the total number of Cell objects significantly, of course there's more overhead since you need to check whether you have a cell of the same value already and need to call the factory method again if you need to update the value of a cell.
Then again all of this could not be worth it if you do not experience any memory/performance problems with your current approach - measuring performance is key here.
Isn't Columns a collection?
var Ids = Columns.Select(c => c.Id).ToArray();
var Names = Columns.Select(c => c.Name).ToArray();
etc. Except why do that if Columns is already a collection? For you could do Columns[index].Id
Or if you must have the code you outlined:
Row newRow = new Row();
newRow.ID = idInfo;
// presuming Cells is a List<>
newRow.Cells.AddRange(Columns.Select(c => new Cell(c.Id)));
Rows.Add(newRow);
Some suggestions (depends on what you are looking for)
Consider using (strongly typed) DataSet/DataTable
If using List and you know the size, set the capacity to avoid reallocation (new List(2000))
Use struct instead of class if it makes sense
Cache objects if it makes sense (instead of duplicating the same object over and over)
You're creating the cells anyways. So I gather that the question refers to when you will fill the cells with their values, which are always in each column for all rows.
I actually think that from a correctness point of view, it makes sense to have the data duplicated, since they are in effect separate instances of the same data.
That said, if it is not really data, but you just want to show a view-column with the same value for each row, and you just want it as a data column in order to ease showing it as a view-column, then in your property-get Row.Cells(Id) you can check the ID, and if it's one of those columns where the value is always the same, return that value, bypassing looking up your _Cells collection.
If the data is mostly the same and sometimes different, you may want to use 'default values' where if the Cell object does not exist, a default value for that column will be returned. This necessitates a GetValue() method on the row, though, if you want to avoid having the Cell object altogether for places where it is default.
If you don't care about #1, you can really make a single instance of whatever the value is, and reference it in your Cell's value. This is harder to do for a Value Type than for a Reference Type (definition here) but it can be done.
Lastly, is there any reason you're not using .NET's supplied DataTable and DataRow types? I'm sure the MS geeks programmed as much efficiency as they could into those.
I have a List<object[]> MyCollection which is a result of a SELECT SQL query.
Each object[] represents a row in the query result, and the length of the array will vary for different queries.
I have the name of the column headers in a separate List<string> MyHeaders.
I want to databind MyCollection to a DataGrid with the header of the columns from MyHeaders, and autogenerate the columns.
The reason I want to use AutoGenerateColumns is because I want the Datagrid to reconize the DataTypes of each object, and use the appropriate Column Templates for each DataType.
Thanks!
If you're stuck and need to get on: use a dataset/ datatable. Ancient but they still work fine! If you want to know if it can be done, i don't know. Most examples of binding to an IList I've seen manually loop and create columns.
Regards GJ
Don't use a list for the headers, use a dictionary and use the property names as the keys and put the description as the values. Do a normal blah.DataSource = List and DataBind(). In your itemdatabound event replace the headers with your description by searching the dictionary with something like this:
foreach col in grid.Columns
{
col.Name = dic[col.Name].Value;
}
Let say I'm working on an Excel clone in C#.
My grid is represented as follows:
private struct CellValue
{
private int column;
private int row;
private string text;
}
private List<CellValue> cellValues = new List<CellValue>();
Each time user add a text, I just package it as CellValue and add it into cellValues. Given a CellValue type, I can determine its row and column in O(1) time, which is great. However, given a column and a row, I need to loop through the entire cellValues to find which text is in that column and row, which is terribly slow. Also, given a text, I too need to loop through the entire thing. Is there any data structure where I can achive all 3 task in O(1) time?
Updated:
Looking through some of the answers, I don't think I had found one that I like. Can I:
Not keeping more than 2 copies of CellValue, in order to avoid sync-ing them. In C world I would have made nice use of pointers.
Rows and Columns can be dynamically added (Unlike Excel).
I would opt for a sparse array (a linked list of linked lists) to give maximum flexibility with minimum storage.
In this example, you have a linked list of rows with each element pointing to a linked list of cells in that row (you could reverse the cells and rows depending on your needs).
|
V
+-+ +---+ +---+
|1| -> |1.1| ----------> |1.3| -:
+-+ +---+ +---+
|
V
+-+ +---+
|7| ----------> |7.2| -:
+-+ +---+
|
=
Each row element has the row number in it and each cell element has a pointer to its row element, so that getting the row number from a cell is O(1).
Similarly, each cell element has its column number, making that O(1) as well.
There's no easy way to get O(1) for finding immediately the cell at a given row/column but a sparse array is as fast as it's going to get unless you pre-allocate information for every possible cell so that you can do index lookups on an array - this would be very wasteful in terms of storage.
One thing you could do is make one dimension non-sparse, such as making the columns the primary array (rather than linked list) and limiting them to 1,000 - this would make the column lookup indexed (fast), then a search on the sparse rows.
I don't think you can ever get O(1) for a text lookup simply because text can be duplicated in multiple cells (unlike row/column). I still believe the sparse array will be the fastest way to search for text, unless you maintain a sorted index of all text values in another array (again, that can make it faster but at the expense of copious amounts of memory).
I think you should use one of the indexed collections to make it work reasonably fast, the perfect one is the KeyedCollection
You need to create your own collection by extending this class. This way your object will still contain row and column (so you will not loose anything), but you will be able to search for them. Probably you will have to create a class encapsulating (row, column) and make it the key (so make it immutable and override equals and get hash code)
I'd create
Collection<Collection<CellValue>> rowCellValues = new Collection<Collection<CellValue>>();
and
Collection<Collection<CellValue>> columnCellValues = new Collection<Collection<CellValue>>();
The outer collection has one entry for each row or column, indexed by the row or column number, the inner collection has all the cells in that row or column. These collections should be populated as part of the process that creates new CellValue objects.
rowCellValues[newCellValue.Row].Add(newCellValue);
columnCellValues[newCellValue.Column].Add(newCellValue);
This smells of premature optimization.
That said, there's a few features of excel that are important in choosing a good structure.
First is that excel uses the cells in a moderately non-linear fashion. The process of resolving formulas involves traversing the spreadsheets in effectively random order. The structure will need a mechanism of easily looking up values of random keys cheaply, marking them dirty, resolved, or unresolvable due to circular reference. It will also need some way to know when there are no more unresolved cells left, so that it can stop working. Any solution that involves a linked list is probably sub-optimal for this, since they would require a linear scan to get those cells.
Another issue is that excel displays a range of cells at one time. This may seem trivial, and to a large extent it is, but It will certainly be ideal if the app can pull all of the data needed to draw a range of cells in one shot. part of this may be keeping track of the display height and width of the rows and columns, so that the display system can iterate over the range until the desired width and height of cells has been collected. The need to iterate in this manner may preclude the use of a hashing strategy for sparse storage of cells.
On top of that, there are some weaknesses of the representational model of spreadsheets that could be addressed much more effectively by taking a slightly different approach.
For example, column aggregates are sort of clunky. A column total is easy enough to implement in excel, but it has a sort of magic behavior that works most of the time but not all of the time. For instance, if you add a row into the aggregated area, further calculations on that aggregate may continue to work, or not, depending on how you added it. If you copy and insert a row (and replace the values) everything works fine, but if you cut and paste the cells one row down, things don't work out so well.
Given that the data is 2-dimensional, I would have a 2D array to hold it in.
Well, you could store them in three Dictionaries: two Dictionary<int,CellValue> objects for rows and columns, and one Dictionary<string,CellValue> for text. You'd have to keep all three carefully in sync though.
I'm not sure that I wouldn't just go with a big two-dimensional array though...
If it's an exact clone, then an array-backed list of CellValue[256] arrays. Excel has 256 columns, but a growable number of rows.
If rows and columns can be added "dynamically", then you shouldn't store the row/column as an numeric attribute of the cell, but rather as a reference to a row or column object.
Example:
private struct CellValue
{
private List<CellValue> _column;
private List<CellValue> _row;
private string text;
public List<CellValue> column {
get { return _column; }
set {
if(_column!=null) { _column.Remove(this); }
_column = value;
_column.Add(this);
}
}
public List<CellValue> row {
get { return _row; }
set {
if(_row!=null) { _row.Remove(this); }
_row = value;
_row.Add(this);
}
}
}
private List<List<CellValue>> MyRows = new List<List<CellValue>>;
private List<List<CellValue>> MyColumns = new List<List<CellValue>>;
Each Row and Column object is implemented as a List of the CellValue objects. These are unordered--the order of the cells in a particular Row does not correspond to the Column index, and vice-versa.
Each sheet has a List of Rows and a list of Columns, in order of the sheet (shown above as MyRows and MyColumns).
This will allow you to rearrange and insert new rows and columns without looping through and updating any cells.
Deleting a row should loop through the cells on the row and delete them from their respective columns before deleting the row itself. And vice-versa for columns.
To find a particular Row and Column, find the appropriate Row and Column objects, then find the CellValue that they contain in common.
Example:
public CellValue GetCell(int rowIndex, int colIndex) {
List<CellValue> row = MyRows[rowIndex];
List<CellValue> col = MyColumns[colIndex];
return row.Intersect(col)[0];
}
(I'm a little fuzzy on these Extension methods in .NET 3.5, but this should be in the ballpark.)
If I recall correctly, there was an article about how Visicalc did it, maybe in Byte Magazine in the early 80s. I believe it was a sparse array of some sort. But I think there were links both up-and-down and left-and-right, so that any given cell had a pointer to the cell above it (however many cells away that may be), below it, to the left of it, and to the right of it.
In a DataGridView bound to a DataView, where cells in a column will contain one of two images from an ImageList (e.g. a green 'online' image or a red 'offline' image), how can you sum the number of occurences of each image when iterating through the DataGridView's rows?
The Value and FormattedValue properties of DataGridViewImageCell return different references even though the entries in the underlying DataTable were created by referencing the same Image from the ImageList.
So rather than it counting 4 occurences of 'online' and 6 occurences of 'offline', I'm getting 10 occurences of alledgedly different images.
Given the description, the best I can suggest is to manually track the image key/index in the .Tag of the cell, and then run your distinct count on the .Tag. Alternatively, if you also have the data in a list/collection, count the data from the original source.
[update following reply]
Since the data is data-bound, you should be able to iterate the .Rows of the DataGridView, obtaining the .DataBoundItem of each. Then for each underlying object, you should be able to obtain the actual property value using TypeDescriptor:
string propName = col.DataPropertyName;
// could also be a dictionary/hashset etc
// could be typed if you know the type
List<object> values = new List<object>();
foreach(DataGridViewRow row in dgv.Rows)
{
object obj = row.DataBoundItem;
// could be typed (via cast) if you know the type
object val = TypeDescriptor.GetProperties(obj)[propName].GetValue(obj);
if (!values.Contains(val))
{
values.Add(val);
}
}
That any help?