从SQL Server读取-需要从CSV读取

Question

At the moment, I source my data from a SQL serve r(2008) database. The cyurrent method is to use a DataTable, which is then passed around and used.

    if (parameters != null)
    {
        SqlDataAdapter _dataAdapter = new SqlDataAdapter(SqlQuery, CreateFORSConnection());
        foreach (var param in parameters)
        {
            _dataAdapter.SelectCommand.Parameters.AddWithValue(param.Name, param.Value);
        }
        DataTable ExtractedData = new DataTable(TableName);
        _dataAdapter.Fill(ExtractedData);
        return ExtractedData;
    }
    return null;

But now, the user has said that we can also get data from txt files, which have the same structure as the tables in SQL Server. So, if I have a table called 'Customer', then I have a csv file with Customer. with the same column structure. The first line in the CSV is the column name, and matches my tables.

Would it be possible to read the txt file into a data table, and then run a SELECT on that data table somehow? Most of my queries are single table queries:

SELECT * FROM Table WHERE Code = 111

There is, however, ONE case where I do a join. That may be a bit more tricky, but I can make a plan. If I can get the txt files into data tables first, I can work with that.

Using the above code, can I not change the connection string to rather read from a CSV instead of SQL Server?

Answer 1

First, you'll need to read the CSV data into a DataTable. There are many CSV parsers out there, but since you prefer using ADO.NET, you can use the OleDB client. See the following article.

http://www.switchonthecode.com/tutorials/csharp-tutorial-using-the-built-in-oledb-csv-parser

Joining is a bit harder, since both sets of data live in different places. But what you can do is get two DataTables (one from each source), then use Linq to join them.

Inner join of DataTables in C#

Answer 2

You could read the text file into a List<string> (if there is just 1 column per file), and then use LINQ to query the list. For example:

var result = from entry in myList
    where entry == "111"
    select entry;

Of course, this example is kind of useless since all you get back is the same string you are searching for. But if there are multiple columns in the file, and they match the columns in your DataTable , why not read the file into the data table, and then use LINQ to query the table?

Here is a simple tutorial about how to use LINQ to query a DataTable: http://blogs.msdn.com/b/adonet/archive/2007/01/26/querying-datasets-introduction-to-linq-to-dataset.aspx