Data Base as a variable

Question

Is there some way in ADO.Net I can use retrieve an item from a data base and use it as a variable in code rather than as data for a control?

jshepler · Answer

Ah! Ok, now I understand... Yes, you can put values from a database into variables to be used. For example (assuming MS-SQL): SqlConnection conn = new SqlConnection(yourconnectionstringhere); SqlCommand cmd = conn.CreateCommand(); SqlDataReader reader; object value; string sCol1, sCol2; // if you are just returning a single value, you can use .ExecuteScalar() cmd.CommandText = "SELECT somecolumn FROM sometable WHERE someID = " + ID; conn.Open(); value = cmd.ExecuteScalar(); // ExecuteScalar() returns an object - which you can cast conn.Close(); // if you returning multiple rows and/or multiple columns, use the data reader cmd.CommandText = "SELECT col1, col2 FROM sometable ORDER BY col1"; conn.Open(); reader = cmd.ExecuteReader(); // don't close the connection until you are done with the reader // loop through working with the data until the end of the recordset is reached while (reader.Read()) { sCol1 = (string)reader["col1"]; sCol2 = (string)reader["col2"]; ... // do some work here with the values ... } conn.Close(); // closing the connection closes the reader indirectly If you need to keep the data around for other uses, consider using a DataSet instead of a data reader. There are MANY ways of accessing and using the data retrieved from a database. Read up on the Command (SqlCommand or OdbcCommand), DataReader (SqlDataReader or ObdcDataReader), and DataSet (just DataSet) objects. In this conext, ignore anything that has to do with databinding (putting data from a database into controls) since that is not what you are interested in.

blair · Answer

> My ambition is fairly simple. I can perform one variation on an action if variable X = one thing and perform another variation is X = something else. I don't want to display X for the user, it is purely an internal control. So what I'd like to do is have some code that says: retrieve X from a database if X = 1, perform action 1 else perform action 2. This seems pretty straightforward in working with a DBMS, but appears to be more complicated when working online. All the books I've seen on ASP.NET talk about getting data into controls, but not about using it behind the scenes.

jshepler · Answer

If I understand you correctly, you can get away with it by using a NameValueCollection object where each item in the collection is indexed by a string value. Other than something like that, it is impossible to do what you want - how would you know what to type in as a variable name while writing your code? Maybe if you explain what it is you're trying to do we could give better advice.

Andrzej Wegierski · Answer

Like Clipper? table->field? No. But You can get single field using ExecuteScalar() method of Command object (OleDbCommand for instance). It's slow if You get many fields but usable to get only one.

Data Base as a variable

Answers (4)