Question: I'm trying to check a TSV of results and want to see how many times F and S come up (for failure or success) however I'm not sure how to doing this counting, or how to having it search the file

I've come across something that is sort of what I'm looking for: [Python Program how to count number of times the letter c shows up](https://stackoverflow.com/questions/13103148/python-program-how-to-count-number-of-times-the-letter-c-shows-up)

```
def countletter(S, F): 
    count = 0
    for x in S:
        if x.lower() == F.lower():
            count += 1
    return count

print (countletter("abcdefFf","F"))

```

But it isn't perfect and I'm not sure how to make it search the file.

Answer: 
Sorry - I know this is an indirect answer, although I would recommend you follow on. I personally have very bad experiences with Excel Interop services (ASP.NET application). As I am aware Microsoft [does not recommend Interop server automation](https://support.microsoft.com/en-us/kb/257757?wa=wsignin1.0).

Even if you solve this issue you might stumble into issues with memory leakage, performance etc. In my previous project we were advanced with Excel interop automation until deployment. We stumbled into so many issues (Excel Interop processes not closing properly etc.) that we had to rewrite everything to OpenXML.

**If possible use the new OpenXML format.** There is a [ClosedXML library](https://closedxml.codeplex.com/) that makes working with very easy.

**Why OpenXML vs Interop?:**

1. Efficiency (OpenXML is lightweight)
2. No memory leakage risk
3. Ease of use
We have converted our Client / Server solution from 4GL language to C#, where embedded C# code below worked without any issue before, and started to receive same error message.

```
Excel.Application excelApp = new Excel.Application();
Excel.Workbook excelWorkbook = excelApp.Workbooks.Open(fileExcel,
    0, false, 5, "", "", false, Excel.XlPlatform.xlWindows, "",
    true, false, 0, true, false, false);

```

I have followed all the instructions in this thread, but to no avail, until I have realised that in our case at least fileExcel, which contains the full path with the name of the file and defined as `System.String fileExcel` had trailing spaces, e.g. instead of "C:\temp\MyTest.xls" it was "C:\temp\MyTest.xls[many many spaces]". 
Once I have added `Trim()` to fileExcel as below, all went back to normal. Hope it will help to someone in the future.

```
Excel.Workbook excelWorkbook = excelApp.Workbooks.Open(fileExcel.Trim(),
    0, false, 5, "", "", false, Excel.XlPlatform.xlWindows, "",
    true, false, 0, true, false, false);

```