Problem

When I retrieve the value of a cell which has a Date format in Excel, I do not get the formatted Date; I get a number. How do I retrieve the formatted Date instead?

Solution

Excel Dates are stored in a “serial date format” behind-the-scenes. So, for example, 2/4/2004 is stored as 38021 in Excel. This number represents the number of days elapsed since January 1, 1900.

When you display a Date in Excel, a built-in conversion is performed which converts this serial format into a string for display in the cell depending on the format you apply to that cell.

More information on Excel Serial Dates can be found at http://www.cpearson.com/excel/datetime.htm.

If you want to use a Date from a cell in your code, all you will be able to retrieve is the serial value of this Date. To use it as a formatted string you will have to convert it.

A set of conversion methods can be found at Code Project.

You will need to use one of them in your application in order to convert the serial value of the date to a formatted string. Once you have a formatted string, you can also create a Date object in .NET (using Convert.ToDateTime() for example) and use the built in .NET Date functions if desired.

A simple example in VB.NET

This example retrieves a serial date from an Excel cell and uses a VB.NET version of the ExcelSerialDateToDMY() method from The Code Project to convert it to its day, month, and year components. To run this example, you would call ReadDate() from the PageLoad event or a ButtonClick event, for example. ReadDate() reads the Date (in serial date format) from cell “E1” of sample2.xls. It then calls ExcelSerialDateToDMY() to retrieve the converted day, month, and year values of the date. It then creates a new .NET Date object using those values. Finally, it writes the .NET Date’s short string value to the Response, so you can see that the correct values were retrieved.

Private Sub ReadDate()
'Create Application object and load Excel file from disk
Dim xlw As New SAExcelApplicationDotNet xlw.Open(Server.MapPath("./sample2.xls"), False)
Dim sheet As SAWorksheet sheet = xlw.Worksheets(1)

'Read cell E1, it's a date
Dim sd As Integer = sheet.Cells("E1").Value
' The following 3 variables are used as "output" parameters to the ExcelSerialDateToDMY()
' method, since the method uses the parameters By Reference, not By Value.
Dim d As Integer ' Will contain the day as an Integer
Dim m As Integer ' Will contain the month as an Integer
Dim y As Integer ' Will contain the year as an Integer

' Retrieve the day, month, and year values of the serial date.
ExcelSerialDateToDMY(sd, d, m, y)

' Create a new .NET Date object with the retrieved values, and display it on the page.
Dim dt As Date = New Date(y, m, d)
Response.Write(dt.ToShortDateString)
End Sub

Private Sub ExcelSerialDateToDMY(ByRef nSerialDate As Integer, ByRef nDay As Integer, _
ByRef nMonth As Integer, ByRef nYear As Integer)
' This function is courtesy of The Code Project.
' http://www.codeproject.com/datetime/exceldmy.asp?df=100&forumid=4548&exp=0&select=590906

' nSerialDate is the serial date from Excel
' nDay, nMonth, and nYear are the "output parameters" where the method will store
' the Day, Month, and Year values as Integers that it extracts from nDate

' Excel/Lotus 123 have a bug with 29-02-1900. 1900 is not a
' leap year, but Excel/Lotus 123 think it is...
If nSerialDate = 60 Then
nDay = 29
nMonth = 2
nYear = 1900
Return
ElseIf nSerialDate < 60 Then
' Because of the 29-02-1900 bug, any serial date
' under 60 is one off... Compensate.
nSerialDate = nSerialDate + 1
End If

' Modified Julian to DMY calculation with an addition of 2415019
Dim l As Integer = nSerialDate + 68569 + 2415019
Dim n As Integer = CInt(Fix((4 * l) / 146097))
l = l - CInt(Fix((146097 * n + 3) / 4))
Dim i As Integer = CInt(Fix((4000 * (l + 1)) / 1461001))
l = l - CInt(Fix((1461 * i) / 4)) + 31
Dim j As Integer = CInt(Fix((80 * l) / 2447))
nDay = l - CInt(Fix((2447 * j) / 80))
l = CInt(Fix(j / 11))
nMonth = j + 2 - (12 * l)
nYear = 100 * (n - 49) + i + l
End Sub

Problem

In the creation of an Excel workbook, sometimes a column contains numerical values stored as strings. For example, a percent column can display percents as strings. This poses a problem if you want to use these values for equations, or if you want to clean up the display of the file, as Excel will mark these strings with a green corner indicating that they can be displayed as numerals, along with a warning message: “The number in this cell is stored as text or preceded by an apostrophe.”

Solution

ExcelApplication allows you to change the NumberFormat of a column so that it will automatically format numerals. This alone is not enough to change the strings into formatted numerals, though, as you must trim any characters off the strings and convert them to doubles to be handled correctly by Excel.

Hence, converting the values for an entire column requires three steps:

1. Gather the values from the column into a collection and convert them to numeric values.
2. Apply the desired Number Format to the styles of column.
3. Cycle through the collection and add the values back to each cell of the column.

For a code example of the three steps outlined above, please see the sample in our documentation for how to Convert strings to formatted numerical values.

Problem

Importing numbers with leadings zeros, such as zip codes and social security numbers, can pose a challenge. While these numbers are most often stored in a database as strings, they can be imported into Excel as either numbers or strings. Importing as numbers is the preferred option, as importing as strings will cause Excel to display a warning message that a number is being displayed as text.

Solution

When importing numbers with leading zeros, you have two options:

1. Import or insert the values as numbers and not as strings. Set the appropriate special format as needed to display the desired number of leading zeros. This is the recommended practice.
2. Import or insert the values as strings. Format the cells as General or Text. Excel will display a warning on each cell that a number is displayed as text. However, the cell values will contain the leading zeros.

Option 1: Import numbers with leading zeros as numbers (Recommended)

As mentioned above, the preferred option for importing numbers with leading zeros as numbers. Leading zeros will be stripped off, as numeric data types cannot contain leading zeros. To display the desired number of leading zeros within Excel on these numeric values, the appropriate formatting string should be set on the cells which contain the data.

It should be noted that a limitation to this approach is that when a value is read out of a cell there will be no leading zeros. If you would prefer to have leading zeros stored in the cell values (and have Excel display the warning message instead), you should use Option 2 as described below.

ExcelTemplate

When using ExcelTemplate, you have three options for converting your data from strings to an appropriate numeric data type. You can:

• Let ExcelTemplate attempt to globally convert all strings to numeric values where appropriate. (This is the default behavior.)
• Convert the applicable zip code values (and any other numbers) to numeric data types through native features of the language. Then set the PreserveStrings property to true to force ExcelTemplate to preserve all strings as strings. This approach will result in the most predictable results, since setting PreserveStrings to true will prevent ExcelWriter from performing string to numeric data type conversions.
• Use a combination of Preserve and/or Convert data marker modifiers on specific columns. Which modifiers you use should depends on how PreserveStrings is set. If you choose this option, the recommended practice is to set PreserveStrings to true and use Convert data marker modifiers on zip code columns. For more info about data marker modifiers, please refer to the Creating Data Markers documentation.

Then set the appropriate cell formats on the template for the columns which will contain these values. Use the Zip Code or Social Security formats (listed under the Special category), or use your own custom string.

ExcelApplication

With ExcelApplication, no automatic string to number conversion exists. Therefore, you must convert the applicable zip code data using native features of the language. Set the appropriate cell formats on the existing file, if there is one, or use the ExcelApplication API to set it on an Area, Range, or individual Cell.

When setting the formatting through the ExcelApplication API, you should use the Style.NumberFormat property. For example, to set a zip code format on a cell, you would do:

 myCell.Style.NumberFormat = NumberFormat.Special_EN_US.ZipCode; 

In the above example, the NumberFormat.SpecialENUS.ZipCode constant is equivalent to “00000”. This forces Excel to always display five digits, prepending zeros to the number as necessary.

Option 2: Import numbers with leading zeros as strings

As mentioned above, you can import numbers with leading zeros as strings instead of converting them to numbers. However, Excel will display a warning that a number is displayed as text. This will allow you store the leading zeros in the cell values, preventing the need to set a special cell format, and also allowing the value to be read from the cell so that it includes the leading zero.

ExcelTemplate

To preserve strings using ExcelTemplate, use a combination of the following techniques:

• Set the global PreserveStrings property to true.
• Use a combination of Preserve and/or Convert data marker modifiers on specific columns. Which modifiers you use depends on how PreserveStrings is set.

Set the applicable cell formats to General or Text in the template.

For more information about using ExcelTemplate to convert strings to numbers where appropriate, please see this post: How to preserve strings with ExcelTemplate.

ExcelApplication

To preserve string values with ExcelApplication, no action is needed. ExcelApplication will always preserve strings, because it provides no automatic conversion functionality.

Set the appropriate cell formats to General or Text, either on the template or using the ExcelApplication API. The following example sets a cell format to Text:

 myCell.Style.NumberFormat = "@";

Problem

ExcelWriter supports the insertion of horizontal and vertical page breaks within a Worksheet using the ExcelApplication class/object. This post covers how to insert page breaks in a worksheet.

Solution

• Worksheet.InsertHorizontalPageBreak – inserts a horizontal page break
• Worksheet.InsertVerticalPageBreak – inserts a vertical page break

C# Example


//--- The following namespace has been imported:
//--- SoftArtisans.OfficeWriter.ExcelWriter

//--- Instantiate ExcelApplication and create a new Workbook
ExcelApplication xla = new ExcelApplication();
Workbook wb = xla.Create();
Worksheet sheet1 = wb.Worksheets[0];

//--- Insert horizontal page break below cell A15
sheet1.InsertHorizontalPageBreak(sheet1.Cells["A15"]);

//--- Insert vertical page break to the right of cell H1
sheet1.InsertVerticalPageBreak(sheet1.Cells["H1"]);

//--- Save Workbook
xla.Save(wb, Response, "out.xls", false);