C# how to get data from server database

Question

How to get data from server database (SQL Server)? The scenario, client press the download button then the data from the server that has been queried (SELECT) and the result is sent to the client over HTTP (Internet). What is the best way to do this?

My way, I use Web Service to select data and send it to the client (the data is sent in string form), the problem I think when I select the whole data, this can make transfer data become slow, is that true?

Answer 1

The easiest way is probably through a .NET web application, although there are libraries for numerous other languages including PHP.

For example, if you had a form with field 'query' submit to this page:

<%

// Get user's query
string query = Request.Form["query"]; // or Request.QueryString for data from the querystring

// Connect to the database    
string connString = "your connection string";
System.Data.SqlClient.SqlConnection conn = new System.Data.SqlClient.SqlConnection(connString);
System.Data.SqlClient.SqlCommand command = new System.Data.SqlClient.SqlCommand(query, conn);
// Read your data however you like
System.Data.SqlClient.SqlDataReader reader = command.ExecuteReader();

while (reader.Read()) {
    // Deal with your data here
    Response.Write(reader.GetString(0));
}

%>

The simplest way to output the data would be using Response.Write(), but you can also use more sophisticated controls. It seems like you just need to output raw results, so Response.Write() may work best.

Of course, the more data you are sending, the longer it will take. However, using a web service shouldn't be slower than any other solution.

Answer 2

My way, I use Web Service to select data and send it to the client (the data is sent in string form), the problem I think when I select the whole data, this can make transfer data become slow, is that true?

Yes, do not, under any circumstance, ever write

Select * From TableName