如何从数据集中检索特定列？

Question

Here's the lines that are querying the database.

string sql = "SELECT col1, col2, col3, col4, col5"
           + "FROM MyTable"
           + "WHERE condition";

DataSet standardResults = SqlHelper.ExecuteDataset(
    m_ConnectionString,
    CommandType.Text,
    sql);

For each column, I'd like to select col1 and col5 .

I'm trying to hover over the dataset object or drill down the content, but I can't figure out where the data I need are located.

Thanks for helping.

Answer 1

From the code you have posted, I can assume that the SqlHelper.ExecuteDataset returns a DataSet . A DataSet contains a collection of DataTables and you can use a index to get them. In your case there would be only one DataTable , since you have the results of one query. So standardResults.DataTables[0] would be associated with the DataTable where your data are in. That being said, I think that you can fairly query your DataTable with LINQ and get that you want. Something like this:

var results = standardResults.DataTables[0]
                             .AsEnumerable()
                             .Select(item=>new 
                             {
                                Col1 = x.Field<string>("col1"),
                                Col5 = x.Field<string>("col5")    
                             });

However, I have to point out that I don't see the reason of selecting the extra columns, col2 , col3 and col4 . If you don't need them, why they are in the select statement?