Using Excel library and Csv library to read .csv, .xls, and .xlsx files respectively, the experience is inconsistent, and there are even logic errors.

[lileyzhao]

Using only a simple two-row, two-column table, create .xlsx, .xls, and .csv files. e.g.

name	age
nike	18

Here are the reading codes and output results for the three formats.： default options: xls file

using ExcelDataReader xls = ExcelDataReader.Create("d://dowhile.xls");
do
{
    var name = xls.GetString(0);
    var age = xls.GetString(1);
    Console.WriteLine($"{name}-{age}");
} while (xls.Read());

xls file output

nike 18
nike 18

xlsx file

using ExcelDataReader xls = ExcelDataReader.Create("d://dowhile.xlsx");
do
{
    var name = xls.GetString(0);
    var age = xls.GetString(1);
    Console.WriteLine($"{name} {age}");
} while (xls.Read());

xlsx file output

name age
nike 18

csv file

using var csv = CsvDataReader.Create("d://dowhile.csv");
do
{
    var name = csv.GetString(0);
    var age = csv.GetString(1);
    Console.WriteLine($"{name} {age}");
} while (csv.Read());

csv file output

nike 18
nike 18

---

if option hasHeader=false Another scenario.

xls file

using ExcelDataReader xls = ExcelDataReader.Create("d://dowhile.xls", new ExcelDataReaderOptions { Schema = ExcelSchema.NoHeaders });
do
{
    var name = xls.GetString(0);
    var age = xls.GetString(1);
    Console.WriteLine($"{name}-{age}");
} while (xls.Read());

xls file output

name age
name age
nike 18

xlsx file

using ExcelDataReader xls = ExcelDataReader.Create("d://dowhile.xlsx", new ExcelDataReaderOptions { Schema = ExcelSchema.NoHeaders });
do
{
    var name = xls.GetString(0);
    var age = xls.GetString(1);
    Console.WriteLine($"{name} {age}");
} while (xls.Read());

xlsx file output

name age
nike 18

csv file

using var csv = CsvDataReader.Create("d://dowhile.csv", new CsvDataReaderOptions { HasHeaders = false });
do
{
    var name = csv.GetString(0);
    var age = csv.GetString(1);
    Console.WriteLine($"{name} {age}");
} while (csv.Read());

csv file output

name age
name age
nike 18

[MarkPflug]

You're observations are probably correct, but based on unexpected/incorrect usage of the library. You should always call Read before accessing fields with GetString, etc. If you change all the code examples from do/while to while(reader.Read()) the behavior should be consistent.

I should modify all the libraries to throw an InvalidOperationException if any field is accessed before Read is called, to indicate that this is not an expected access pattern.

[lileyzhao]

You are right, I have now switched to using while(read()) to resolve the inconsistency issue. In fact, initially I was using while(read()), but I tried using do-while due to another very exceptional problem. I will submit another very exceptional problem shortly, please wait.

[MarkPflug]

I will leave this issue open as a reminder that I should make GetString et al throw when the reader hasn't yet been advanced (before Read) or after the end of the data has been reader when Read returns false.

[lileyzhao]

I have submitted a new issue, please take a look there for the root cause of the problem.

[MarkPflug]

This is fixed in 0.4.20, just pushed to nuget.