在C＃中读取CSV时如何将科学计数法值解析回原始值

Question

I am working on a weather map application that imports csv files via a url. The date fields inside the csv are stored as a string like 201601280330, which would be today's date 1/28/2016 3:30. However, when reading the csv via a streamreader the value is coming back in scientific notation like 2.01601E+11. Nothing I have tried seems to return the whole value 201601280330.

For example:

var date = "2.01601E+11"; var d = Decimal.Parse(date, System.Globalization.NumberStyles.Float);

returns 201601000000 chopping off the remaining part of the string. Does anyone know a way to return the full value. When I save the csv locally as a text file the correct value 201601280330 is saved rather than 2.01601E+11 . Anyway to get this in the code without having to save first? I am using the code below to read the csv file.

    public static DataTable GetDataTableFromCSVFile(string path)
    {
        DataTable dt = new DataTable();
        try
        {
            using (StreamReader sr = new StreamReader(path))
            {
                string[] headers = sr.ReadLine().Split(',');

                foreach (string header in headers)
                {
                    if (header.Contains("ERROR:"))
                    {
                        return null;
                    }

                    dt.Columns.Add(header);
                }
                while (!sr.EndOfStream)
                {
                    string[] rows = sr.ReadLine().Split(',');
                    DataRow dr = dt.NewRow();
                    for (int i = 0; i < headers.Length; i++)
                    {
                        dr[i] = rows[i];
                    }
                    dt.Rows.Add(dr);
                }
            }
        }

EDIT

Although this does not provide a technical answer to the problem I was experiencing it might provide a better explanation and help others if they experience this. Some of the example csv files sent to me for testing had been edited in Excel to make the csv smaller and then saved. After further testing, it looks like the issue occurs only for the csv files edited in Excel. Tentatively, this solves the problem for me since we won't be downloading the csv files and editing them in Excel, rather pulling them straight from a url. The code I posted above will read a the correct value without notation while for the csv edited in Excel it will only read the value with scientific notation. Unless I am wrong, I assume Excel must add something to edited csv files that prevents the value from being read correctly.

Answer 1

My original answer questioned whether you were using Excel, but as you hadn't mentioned that in your question I was rightly told that I was off topic, so I changed it. Now that you have provided a follow-up answer that does mention Excel I have changed it back, here is what I wrote originally:

Once the value has been converted into scientific notation it cannot be converted back. It is a limitation of Excel that is performing this conversion. If, when importing the data you choose a column type of Text (rather than General), then the data will be imported verbatim and Excel won't convert it into scientific notation.

As I suspected, it is Excel (not your code) that is changing the numerical data into scientific notation. I have seen this problem many times and suggest people DO NOT open CSV files using Excel. If you have to, then import rather than open so you can specify the data types of your numerical columns.

Answer 2

Although this does not provide a technical answer to the problem I was experiencing it might provide a better explanation and help others if they experience this. Some of the example csv files sent to me for testing had been edited in Excel to make the csv smaller and then saved. After further testing, it looks like the issue occurs only for the csv files edited in Excel. Tentatively, this solves the problem for me since we won't be downloading the csv files and editing them in Excel, rather pulling them straight from a url. The code I posted above will read a the correct value without notation while for the csv edited in Excel it will only read the value with scientific notation. Unless I am wrong, I assume Excel must add something to edited csv files that prevents the value from being read correctly.