Andrus Andrus - 1 month ago 14
ASP.NET (C#) Question

How to define and enumerate list in web.config

ASP.NET MVC4 application needs reading list from web.config file.

web.config contains

<?xml version="1.0" encoding="utf-8"?>
<configuration>

<configSections>
<sectionGroup name="connectionGroup">
<section
name="connection"
type="Helpers.connectionSection"
allowLocation="true"
allowDefinition="Everywhere"
/>
</sectionGroup>
</configSections>

<connectionGroup>
<connection url="site1" database="db1" />
<connection url="site2" database="db2" />
</connectionGroup>


code to enumerate it is:

IList<ConnectionSection> connection =
(IList<ConnectionSection>)ConfigurationManager.GetSection("connectionGroup");
foreach (var s in connection)
Debug.WriteLine(s.Url);


running it produces error

Parser Error Message: Sections must only appear once per config file. See the help topic <location> for exceptions.

Source Error:

Line 19: <connectionGroup>
Line 20: <connection url="site1" database="site1" />
Line 21: <connection url="site2" database="site2" />
Line 22: </connectionGroup>


How to fix this so that web.config can contain multiple connection elements ?

Section is defined as:

namespace Helpers
{
public class ConnectionSection : ConfigurationSection
{

[ConfigurationProperty("url", IsRequired = true, IsKey = true)]
public string Url
{
get { return (string)this["url"]; }
set { this["url"] = value; }
}

[ConfigurationProperty("database", DefaultValue = "mydb", IsRequired = false)]
public string Database
{
get { return (string)this["database"]; }
set { this["database"] = value; }
}
}
}

Answer
public class ConnectionGroupConfigurationSection : ConfigurationSection
{
    public const string NodeName = "connectionGroup";

    [ConfigurationProperty("", IsDefaultCollection=true)]
    public ConnectionGroupConfigurationElementCollection ConnectionGroup
    {
        get { return (ConnectionGroupConfigurationElementCollection)this[""]; }
    }
}

public class ConnectionGroupConfigurationElementCollection : ConfigurationElementCollection
{
    protected override ConfigurationElement CreateNewElement()
    {
        return new ConnectionElement();
    }

    protected override object GetElementKey(ConfigurationElement element)
    {
        return (element as ConnectionElement).Id;
    }

    public override ConfigurationElementCollectionType CollectionType
    {
        get { return ConfigurationElementCollectionType.BasicMap; }
    }

    protected override string ElementName
    {
        get { return "connection"; }
    }
}

public class ConnectionElement : ConfigurationElement
{
    [ConfigurationProperty("url", IsRequired=true, IsKey=true)]
    public string Url { get { return (string)this["url"]; } }

    [ConfigurationProperty("database", DefaultValue = "mydb", IsRequired = false)]
    public string Database { get { return (string)this["database"]; } set { this["database"] = value; } }
}