Develop Reference

How to retrieve efficiently all strings from a large Excel documents

The Excel spreadsheet should be read by .NET. It is very efficient to read all values from the active range by using the property Value. This transfers all values in a two dimensional array, by one single call to Excel.
However reading strings is not possible for a range which contains more than one single cell. Therefor we have to iterate over all cells and use the Text property. This shows very poor performance for larger document.
The reason of using strings rather than values is to obtains the correct format (for instance for dates or the number of digits).
Here is a sample code written in C# to demonstrate the approach.
static void Main(string[] args)
{
Excel.Application xlApp = (Excel.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application");
var worksheet = xlApp.ActiveSheet;
var cells = worksheet.UsedRange();
// read all values in array -> fast
object[,] arrayValues = cells.Value;
// create array for text of the same extension
object[,] arrayText = (object[,])Array.CreateInstance(typeof(object),
new int[] { arrayValues.GetUpperBound(0), arrayValues.GetUpperBound(1) },
new int[] { arrayValues.GetLowerBound(0), arrayValues.GetLowerBound(1) });
// read text for each cell -> slow
for (int row = arrayValues.GetUpperBound(0); row <= arrayValues.GetUpperBound(0); ++row)
{
for (int col = arrayValues.GetUpperBound(0); col <= arrayValues.GetUpperBound(1); ++col)
{
object obj = cells[row, col].Text;
arrayText[row, col] = obj;
}
}
}
The question is, if there is a more efficient way to read the complete string content from an Excel document. One idea was to use cells.Copy to copy the content to the clipboard to get it from there. However this has some restrictions and could of course interfere with users which are working with the clipboard at the same time. So I wonder if there are better approaches to solve this performance issue.

You can use code below:
using (MSExcel.Application app = MSExcel.Application.CreateApplication())
{
MSExcel.Workbook book1 = app.Workbooks.Open( this.txtOpen_FilePath.Text);
MSExcel.Worksheet sheet = (MSExcel.Worksheet)book1.Worksheets[1];
MSExcel.Range range = sheet.GetRange("A1", "F13");
object value = range.Value; //the value is boxed two-dimensional array
}
The code is provided from this post. It should be much more efficient than your code, but may not be the best.

C# Efficient way to iterate over excel worksheet

I have the following code:
string result = "";
for(int i=2; i<=excelRange.Rows.Count; i++)
{
result += excelRange.Cells[i, 2].Value2;
}
For an excel file with a couple hundred entries this takes 5 seconds. Is there a more efficient way, perhaps? I only want the values from B2 to Bn.

Yes, there is a more efficient way.
Create a range that exactly matches the cells that you really need.
Get the Value2 property of this range. The result will be an array type.
Iterate through the array
The problem with your approach is the large number of inter-process requests between your application and Excel. Your approach requires two or three requests per cell. The proposed approach is much faster because it requires a few requests up-front but not additional requests per cell.
Note that this works up to about 4000 cells. If you need to process more cells, you will need to split it into several ranges, each one containing less than 4000 cells.
Update
Assuming Excel is already running, it would look something like this (the correct number of rows in the B column is automatically selected):
var excelApp = (Excel.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application");
Excel._Worksheet workSheet = (Excel.Worksheet)excelApp.ActiveSheet;
var range = (Excel.Range)workSheet.Range[workSheet.Range["B2"],
workSheet.Range["B2"].End[Excel.XlDirection.xlDown]];
var cellData = (Object[,])range.Value2;
string result = "";
foreach (var cell in cellData) {
result += cell.ToString();
}

The basic skeleton is the following:
var xlApp = new Excel.Application { Visible = true };
var xlBook = xlApp.Workbooks.Open(#"C:\Temp\Results.xlsx");
var xlSheet = xlBook.Sheets[1] as Excel.Worksheet;
var arr = (object[,])xlSheet.Range["B2:B100000"].Value;
var sb = new StringBuilder();
for (int x = 1; x <= arr.GetUpperBound(0); ++x)
{
sb.Append(arr[x, 1]);
}
var final_string = sb.ToString();
// Close workbook, close Excel...

How to get a value from a dynamic type variable obtained from the "value" property of Microsoft.Office.Interop.Excel.Range object

I have a problem when i'm trying to obtain the values from a dynamic type variable, which is result of the "value" property of Microsoft.Office.Interop.Excel.Range object. This is my scenario:
I'm using c#, and i have this values in an excel document:
11010001 123 0
11010002 0 23
11010003 0 120
When i do a copy with control+c command, i need to capture those values and make something with them, and this is the way that de Range object returns the selected values:
//C# Code
//Get the active and open Excel
var excel = Marshal.GetActiveObject("Excel.Application") as Microsoft.Office.Interop.Excel.Application;
//Get the selected rows range
Range range = excel.Selection as Range;
//Get the values of selected rows
dynamic cellValue = range.Value;
In the cellValue variable i have the values in the following format:
Code fragment
So, my problem is that i don't know how to get those values by separated and insert them in my database.
Could you help me whith a suggestion or code example of how to get those values from the dynamic type variable?
Regards.

After so much trying i found the solution when i put it the dynamic variable into the watch window and right there was the way to access to the values contained, that is the following way:
dynamic cellValue = range.Value;
int longitud = ((object[,])cellValue).Length;
for (int i = 1; i <= longitud/3; i++)
{
for (int j = 1; j <= 3; j++)
{
object texto = ((object[,])cellValue)[i, j];
}
}
but note that you have to import the Microsoft.CSharp.dll and using Microsoft.CSharp.RuntimeBinder; to make possible that work fine.
Regards.

Array not filling with .Split Method

I am having an issue getting the array "whyWontYouWork" to populate with a value. In the following example, the value of rangeNames[j] is "$A$1:$A$10".
the string "group" will fill in correctly as "$A$1:$A$10" but the line above it shows up as "The name 'whyWontYouWork' does not exist in this context", so I am at a loss since it works once, and when I try to split the string, I get nothing. Any ideas?
private void CutStates(string[] sheetNames,string[] rangeNames, string[] idNums)
{
Excel.Application xlApp = (Excel.Application)System.Runtime.InteropServices.Marshal.GetActiveObject("Excel.Application");
Excel.Workbook wkbk = null;
wkbk = xlApp.ActiveWorkbook;
for (int i = 0; i < idNums.Length; i++)
{
string stateId = idNums[i];
for (int j = 0; j < sheetNames.Length; j++)
{
string[] sheet = sheetNames[j].Split('!');
List<string> rowsToDelete = new List<string>();
List<string> reverseDelete = new List<string>();
string tabName = sheet[0];
string[] whyWontYouWork = rangeNames[j].Split(':');
string group = rangeNames[j];
Excel.Range range = wkbk.Sheets[tabName].Range[group];
foreach (Excel.Range cell in range)
{
string val2 = cell.Value.Substring(0, 2);
string cellAdd = cell.Address.ToString();
if (val2 != stateId)
{
string delCell = cell.Address.ToString();
rowsToDelete.Add(delCell);
}
}
reverseDelete = rowsToDelete.ToList();
reverseDelete.Reverse();
foreach (string item in reverseDelete)
{
Excel.Range delete = wkbk.Sheets[tabName].Range[item];
delete.Delete();
}
}//j
}//i
}
I plan on using the first part ($A$1) as the starting point of a group to delete from the top down, and the second part ($A$10) to be the starting point from the bottom up to delete.
I want to iterate through the cells in "group" one at a time and if the first two characters don't match the two character stateId. At that point I move to the next until I find one that matches, move back one row grab that address and then grab the start of the list ($A$1) and select from there to the last row that doesn't match, and delete the block. I will do the same for the row after the last match to the end ($A$10). I would do this line by line but I do this over 15K rows so one at a time is terribly slow. I hope that makes more sense.

From code it seems you are iterating through sheets (for (int j = 0; j < sheetNames.Length; j++)) so it is possible that for first sheet you have rangeNames[j] value ("$A$1:$A$10") and on other sheets you don't.
From what I remember Excel by default creates 3 sheets, so that's probably the problem.

Thanks to A few of you pointing out that the variable wasn't used, I checked my settings and it was optimizing the variable away. I thought I had changed that. Adding a simple console.writeline (instead of using the Watch) pushed the variable into use and made it stick.

Convert multidimensional Array (Object[,]) to string[]

I'm stuck in an easy task: convert an multidimensional Array (Object[,]) in a monodimensional string[].
Long story short: I'm reading an excel file using a com library which returns a dynamic type casted to Object[,] at runtime.
SortedSet<string> rows = new SortedSet<string>();
for (int i = 3; i <= 5; i++)
{
Microsoft.Office.Interop.Excel.Range range = worksheet.get_Range("A"+i, "J"+i);
Array cells = (Array) range.Cells.Value; // value return dynamic [,] -> Object[,] -> cast to Array[,]
string[] rowCells = ConvertArrayToStringArray(cells); //
rows.Add(string.Join("\t", rowCells));
}
return string.Join("\r\n", rows);
Since Array[,] always have 1 row (I read the excel file row by row) I'd like to cast it to a simple string[] (or List) without using another loop in ConvertArrayToStringArray function.
I could read all cells in an action (not row by row like in code above), but I've no idea of how many rows are in excel file.
I appreciate any help

string[] rowCells = cells.Cast<string>().ToArray();