使用 Linq 从 Excel 工作表中读取

Question

How does one convert the following for loop into linq query to use exampleDataList and get the values out of it?

string filename = Server.MapPath("/") + "MyExcelFileData.xlsx";
const int startRow = 1;
IList<double> exampleDataList = new List<double>();
var existingFile = new FileInfo(filename);
enter code here
using (var package = new ExcelPackage(existingFile))
{
    ExcelWorkbook workBook = package.Workbook;
    var currentWorksheet = workBook.Worksheets.First();
    for (int rowNumber = startRow + 1; rowNumber <= currentWorksheet.Dimension.End.Row; rowNumber++)
    {
        var col1Value = Convert.ToDouble(currentWorksheet.Cells[rowNumber, 1].Value);
        exampleDataList.Add(col1Value);
    }
}

Answer 1

First change this:

IList<double> exampleDataList = new List<double>();

to:

List<double> exampleDataList = new List<double>();

There is no need to use interface instead of concrete type for a local variable. Then you'll be able to write:

exampleDataList.AddRange(
    Enumerable.Range(startRow + 1, currentWorksheet.Dimension.End.Row)
    .Select(i => Convert.ToDouble(currentWorksheet.Cells[i, 1].Value)));

You first create an enumeration with numbers from startRow + 1 to currentWorksheet.Dimension.End.Row using Enumerable.Range() helper function. Then you project that sequence to something else using Select() . Lambda just mimic what you did inside your for loop.

If you're learning LINQ stuff I strongly suggest to take a look to EduLINQ articles (from our Jon Skeet). They're well done and you'll understand many details about how it could be implemented.

Edit: as pointed out by rae1n in comment if exampleDataList contains only data from this LINQ query (you don't need to add things before query) then you can use ToList() to convert enumeration returned by Select() directly into a List<double> .