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POHow to pass in a parameter for a class set property (not class declaration)
 

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  1. POHow to pass in a parameter for a class set property (not class declaration)
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    <p><strong>Background:</strong></p> <p>I am making a c# 4.0 class for re-use so I can send one parameter to most methods of my program and pass a ‘Connections’ object that can hold things like:</p> <ul> <li>ConnectionStrings </li> <li>DbConnection (i.e. OleDbConnection or SQLConnection) </li> <li>DataReader (i.e. OleDbDataReader or SQLDataReader)</li> </ul> <p>The reasoning is that I will eventually upgrade to SQL Server and don’t want to change my method parameters or code so much. Methods often have to call a quick query here and there from the same database. </p> <p><strong>Question:</strong></p> <p>How do I properly setup (and call) the right-hand side of the DRMDbConnection ‘set’ parameter for DbType (now hard-coded as integer 1) in the method below at line: </p> <pre><code>set { drmDbConnection = SetDRMDbConnection(1); } </code></pre> <p><strong>Sample Code:</strong></p> <pre><code>public class Connections { public string DRMDbConnectionString { get; set; } private object drmDbConnection; public object DRMDbConnection { get { return drmDbConnection; } set { drmDbConnection = SetDRMDbConnection(1); } } private object SetDRMDbConnection(int DbType) { if (DbType == 1) return new System.Data.OleDb.OleDbConnection(); else return new SqlConnection(); } </code></pre> <p>}</p> <p><strong>EDITED Oct 31</strong></p> <p>I updated the class code to use the recommended IDbConnection, IDbCommand and IDataReader. Note: without a change to the SQL Server connection string you will recieve an error: "There is already an open DataReader associated with this Command which must be closed first." Thus add this to connection string: "MultipleActiveResultSets=True;"</p> <p><strong>Updated Class code</strong></p> <pre><code>public class Connections // reusuable object to hold all database Connections and a convenient DataReader and Command object. // Its purpose is to also be able to handle your choice of database connection, i.e. OleDb or SQL Server. { public string DRMConnectionString { get; set; } public IDbConnection DRMConnection; public IDbCommand DRMCommand { get { return DRMConnection.CreateCommand(); } set { } } public int DRMConnectionType // must be called to setup database connection and command. The connectionstring must be previously set. { set { if (value == 1) DRMConnection = new System.Data.OleDb.OleDbConnection(DRMConnectionString); else DRMConnection = new SqlConnection(DRMConnectionString); } } public void CloseConnections() { if (DRMCommand != null) DRMCommand.Dispose(); if ((DRMConnection != null) &amp;&amp; (DRMConnection.State != ConnectionState.Closed)) DRMConnection.Close(); } } </code></pre> <p><strong>CALLING CODE</strong></p> <pre><code>var conn = new Connections(); conn.DRMConnectionString = "my connection string"; conn.DRMConnectionType = 2; conn.DRMConnection.Open(); try { using (var cmd = conn.DRMCommand) { cmd.CommandText = "SELECT * FROM MyTable"; using (var rdr = cmd.ExecuteReader()) { while (rdr.Read()) { CallSubMethodThatAlsoOpensDataReader(conn); } } } } finally { conn.CloseConnections(); } CallSubMethodThatAlsoOpensDataReader(Connections Conn) { using (var cmd = Conn.DRMCommand) { cmd.CommandText = "SELECT * FROM MyOtherTable"; using (var rdr = cmd.ExecuteReader()) // Error: There is already an open DataReader associated with this Command which must be closed first. { ; // do stuff } } } </code></pre>
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