Sylvan CSV阅读器C#检查CSV中是否缺少列

Question

@MarkPflug我需要读取总共45-85列中的12列这来自多个csv文件(数百个(。但问题是，很多时候，一些csv数据文件中会缺少一两列。如果我使用nuget软件包syvan csv阅读器，我如何在C#中检查csv文件中缺少的列。这里有一些代码：

// Create a reader
CsvDataReader reader = CsvDataReader.Create(file, new CsvDataReaderOptions { ResultSetMode = ResultSetMode.MultiResult });
// Get column by name from csv. This is where the error occurs only in the files that have missing columns. I store these and then use them in a GetString(Ordinal).
reader.GetOrdinal("HomeTeam");
reader.GetOrdinal("AwayTeam");
reader.GetOrdinal("Referee");
reader.GetOrdinal("FTHG");
reader.GetOrdinal("FTAG");
reader.GetOrdinal("Division");
// There is more data here, but anyway you get the point.
// Here I run the reader and for each piece of data I run my database write method.
while (await reader.ReadAsync())
{
await AddEntry(idCounter.ToString(), idCounter.ToString(), attendance, referee, division, date, home_team, away_team, fthg, ftag, hthg, htag, ftr, htr);
}

我尝试了以下方法：

// This still causes it to go out of bounds.
if(reader.GetOrdinal("Division") < reader.FieldCount)
// only if the ordinal exists then assign it in a temp variable
else
// skip this column (set the data in add entry method to "")

Answer 1

查看源代码，如果找不到列名或列名不明确，则GetOrdinal会抛出。因此，我希望你能做到：

int blah1Ord = -1;
try{ blah1Ord = reader.GetOrdinal("blah1"); } catch { }
int blah2Ord = -1;
try{ blah2Ord = reader.GetOrdinal("blah2"); } catch { }
while (await reader.ReadAsync())
{
var x = new Whatever();
if(blah1Ord > -1) x.Blah1 = reader.GetString(blah1Ord);
if(blah2Ord > -1) x.Blah2 = reader.GetString(blah2Ord);
}

等等，所以你可以有效地判断一列是否存在——如果不存在，序数仍然是-1——然后用它来决定是否读取该列

顺便说一句，我一直在处理标题名称不正确/拼写错误/部分错误的CSV，我发现自己得到了列模式并在其中搜索部分，比如：

using var cdr = CsvDataReader.Create(sr);
var cs = await cdr.GetColumnSchemaAsync();
var sc = StringComparison.OrdinalIgnoreCase;
var blah1Ord = cs.FirstOrDefault(c => c.ColumnName.Contains("blah1", sc))?.ColumnOrdinal ?? -1;

Answer 2

我开始使用Sylvan库，它非常强大。不确定这是否对您有帮助，但如果您使用实体的DataBinder.Create<T>通用方法，您可以执行以下操作来获取CSV文件中未映射到任何实体属性的列：

var dataBinderOptions = new DataBinderOptions()
{
// AllColumns is required to throw UnboundMemberException
BindingMode = DataBindingMode.AllColumns,
};
IDataBinder<TEntity> binder;
try
{
binder = DataBinder.Create<TEntity>(dataReader, dataBinderOptions);
}
catch (UnboundMemberException ex)
{
// Use ex.UnboundColumns to get unmapped columnns
readResult.ValidationProblems.Add($"Unmapped columns: {String.Join(", ", ex.UnboundColumns)}");
return;
}