How to convert DataSet to DataTable

Question

I am retrieving data from a SQL table so I can display the result on the page as a HTML table. Later I need to be able to save that table as a CSV file.

So far I have figured out how to retrieve the data and fill them in a dataset for display purpose (which is working perfectly)...

        string selectQuery = "SELECT Name, ProductNumber, ListPrice FROM Poduction.Product";

        // Establish the connection to the SQL database 
        SqlConnection conn = ConnectionManager.GetConnection();
        conn.Open();

        // Connect to the SQL database using the above query to get all the data from table.
        SqlDataAdapter myCommand = new SqlDataAdapter(selectQuery, conn);

        // Create and fill a DataSet.
        DataSet ds = new DataSet();
        myCommand.Fill(ds);

and how to save them in a CSV file with the help of following code from: http://www.evontech.com/login/topic/1983.html

    private void exportDataTableToCsv(DataTable formattedDataTable, string filename)
    {
       DataTable toExcel = formattedDataTable.Copy();
       HttpContext context = HttpContext.Current;
       context.Response.Clear();

       foreach (DataColumn column in toExcel.Columns)
       {
          context.Response.Write(column.ColumnName + ",");
       }

       context.Response.Write(Environment.NewLine);
       foreach (DataRow row in toExcel.Rows)
       {
          for (int i = 0; i < toExcel.Columns.Count; i++)
          {
             context.Response.Write(row.ToString().Replace(",", string.Empty) + ",");
          }

          context.Response.Write(Environment.NewLine);
       }

       context.Response.ContentType = "text/csv";
       context.Response.AppendHeader("Content-Disposition", "attachment; filename=" + filename + ".csv");
       context.Response.End();
    }

Now my problem is how do I convert this DataSet to DataTable? I have tried the way described here with NO luck: http://www.ezineasp.net/post/ASP-Net-C-sharp-Convert-DataSet-to-DataTable.aspx

Can anyone help me?

Solution 1

A DataSet already contains DataTables. You can just use:

DataTable firstTable = dataSet.Tables[0];

or by name:

DataTable customerTable = dataSet.Tables["Customer"];

Note that you should have using statements for your SQL code, to ensure the connection is disposed properly:

using (SqlConnection conn = ...)
{
    // Code here...
}

Solution 2

DataSet is collection of DataTables.... you can get the datatable from DataSet as below.

//here ds is dataset
DatTable dt = ds.Table[0]; /// table of dataset

Comments

[AlwaysANovice]

Thanks for the quick responses! I have already tried this: mySqlAdapter.Fill(myDataSet); DataTable myDataTable = myDataSet.Tables[0]; but the CSV file does not look correct as the values are missing and replaced with "System.Data.DataRow".... Name,ProductNumber,ListPrice, System.Data.DataRow,System.Data.DataRow,System.Data.DataRow, System.Data.DataRow,System.Data.DataRow,System.Data.DataRow, System.Data.DataRow,System.Data.DataRow,System.Data.DataRow, System.Data.DataRow,System.Data.DataRow,System.Data.DataRow, how to fix this?

[Jon Skeet]

@Walahh: Well your CSV code is calling ToString() on DataRow, which looks like a bad idea to me. I suggest you ask about that as a separate question, as it really isn't the same as the question you asked.

[Steam]

@JonSkeet - I am getting a DataSet from SSIS. I execute a SQL server query with ADO.NET connection. The result set is stored in a DataSet. Is there a way I could name my result set such that DataTable for it also gets the same name ? Otherwise, I can use the index.

[Steam]

I was wondering why could one need a collection of DataTables, ie DataSet to store the result sets of a query. A result set is always one table. So, what are the advantages of storing it in a DataSet instead ?

[Jon Skeet]

@blasto: You can issue a multi-result query, although I think it's relatively rare. To be honest I've never liked the "old-school" ADO.NET...

[Steam]

@JonSkeet - Oh yes. I now realized what you mean - the multiple select statements in Management Studio that show multiple result sets in the output/execution window. Makes sense now. I wonder why someone would want to do that.

[Steam]

@JonSkeet - Please tell me why you "never liked the "old-school" ADO.NET". I don't think I can use any other connection now. I dont want to use ADO or OLEDB.

[Jon Skeet]

@blasto: I've always preferred getting things into a strongly-typed form as quickly as possible. Strongly-typed datasets are better than nothing, but I still prefer a proper ORM. (I realize that comes with its own problems, of course...)

[JeffO]

@Steam - Inside the dataset, you can have join logic similar to a database without having to send the data to the database after each incremental change (batch). This could be used to handle referential integrity like in a parent-child relationship.