C# Excel import data from CSV into Excel

Question

How do I import data in Excel from a CSV file using C#? Actually, what I want to achieve is similar to what we do in Excel, you go to the Data tab and then select From Text option and then use the Text to columns option and select CSV and it does the magic, and all that stuff. I want to automate it.

If you could head me in the right direction, I'll really appreciate that.

EDIT: I guess I didn't explained well. What I want to do is something like

Excel.Application excelApp;
Excel.Workbook excelWorkbook;

// open excel
excelApp = new Excel.Application();

// something like
excelWorkbook.ImportFromTextFile(); // is what I need

I want to import that data into Excel, not my own application. As far as I know, I don't think I would have to parse the CSV myself and then insert them in Excel. Excel does that for us. I simply need to know how to automate that process.

Answer 1

I think you're over complicating things. Excel automatically splits data into columns by comma delimiters if it's a CSV file. So all you should need to do is ensure your extension is CSV.

I just tried opening a file quick in Excel and it works fine. So what you really need is just to call Workbook.Open() with a file with a CSV extension.

Answer 2

I beleive there are two parts, one is the split operation for the csv that the other responder has already picked up on, which I don't think is essential but I'll include anyways. And the big one is the writing to the excel file, which I was able to get working, but under specific circumstances and it was a pain to accomplish.

CSV is pretty simple, you can do a string.split on a comma seperator if you want. However, this method is horribly broken, albeit I'll admit I've used it myself, mainly because I also have control over the source data, and know that no quotes or escape characters will ever appear. I've included a link to an article on proper csv parsing, however, I have never tested the source or fully audited the code myself. I have used other code by the same author with success. http://www.boyet.com/articles/csvparser.html

The second part is alot more complex, and was a huge pain for me. The approach I took was to use the jet driver to treat the excel file like a database, and then run SQL queries against it. There are a few limitations, which may cause this to not fit you're goal. I was looking to use prebuilt excel file templates to basically display data and some preset functions and graphs. To accomplish this I have several tabs of report data, and one tab which is raw_data. My program writes to the raw_data tab, and all the other tabs calculations point to cells in this table. I'll go into some of the reasoning for this behavior after the code:

First off, the imports (not all may be required, this is pulled from a larger class file and I didn't properly comment what was for what):

using System.IO;
using System.Diagnostics;
using System.Data.Common;
using System.Globalization;

Next we need to define the connection string, my class already has a FileInfo reference at this point to the file I want to use, so that's what I pass on. It's possible to search on google what all the parameters are for, but basicaly use the Jet Driver (should be available on ANY windows install) to open an excel file like you're referring to a database.

string connectString = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source={filename};Extended Properties=""Excel 8.0;HDR=YES;IMEX=0""";
connectString = connectString.Replace("{filename}", fi.FullName);

Now let's open up the connection to the DB, and be ready to run commands on the DB:

DbProviderFactory factory = DbProviderFactories.GetFactory("System.Data.OleDb");

using (DbConnection connection = factory.CreateConnection())
{
  connection.ConnectionString = connectString;
  using (DbCommand command = connection.CreateCommand())
  {
    connection.Open();

Next we need the actual logic for DB insertion. So basically throw queries into a loop or whatever you're logic is, and insert the data row-by-row.

string query = "INSERT INTO [raw_aaa$] (correlationid, ipaddr, somenum) VALUES (\"abcdef", \"1.1.1.1", 10)";
command.CommandText = query;
command.ExecuteNonQuery();

Now here's the really annoying part, the excel driver tries to detect you're column type before insert, so even if you pass a proper integer value, if excel thinks the column type is text, it will insert all you're numbers as text, and it's very hard to get this treated like a number. As such, excel must already have the column type as the number. In order to accomplish this, for my template file I fill in the first 10 rows with dummy data, so that when you load the file in the jet driver, it can detect the proper types and use them. Then all my forumals that point at my csv table will operate properly since the values are of the right type. This may work for you if you're goals are similar to mine, and to use templates that already point to this data (just start at row 10 instead of row 2).

Because of this, my raw_aaa tab in excel might look something like this: correlationid ipaddr somenum abcdef 1.1.1.1 5 abcdef 1.1.1.1 5 abcdef 1.1.1.1 5 abcdef 1.1.1.1 5 abcdef 1.1.1.1 5 abcdef 1.1.1.1 5 abcdef 1.1.1.1 5 abcdef 1.1.1.1 5

Note row 1 is the column names that I referenced in my sql queries. I think you can do without this, but that will require a little more research. By already having this data in the excel file, the somenum column will be detected as a number, and any data inserted will be properly treated as such.

Antoher note that makes this annoying, the Jet Driver is 32-bit only, so in my case where I had an explicit 64-bit program, I was unable to execute this directly. So I had the nasty hack of writing to a file, then launch a program that would insert the data in the file into my excel template.

All in all, I think the solution is pretty nasty, but thus far haven't found a better way to do this unfortunatly. Good luck!