/*
            using Microsoft.Practices.EnterpriseLibrary.Configuration;
            using Microsoft.Practices.EnterpriseLibrary.Common;
            using Microsoft.Practices.EnterpriseLibrary.Data;
            using Microsoft.Practices.EnterpriseLibrary.Data.Configuration;
            */

            DatabaseSettings dbSetting = ConfigurationManager.GetConfiguration("dataConfiguration") as DatabaseSettings;
            ConnectionStringData defaultConnection = dbSetting.ConnectionStrings[0];
            MessageBox.Show(defaultConnection.Parameters["database"].Value);
            defaultConnection.Parameters["Integrated Security"].Value = "True";
            defaultConnection.Parameters["database"].Value = "111";
            defaultConnection.Parameters["server"].Value = "45345";
            ConfigurationManager.WriteConfiguration("dataConfiguration", defaultConnection);

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <section name="enterpriselibrary.configurationSettings" type="Microsoft.Practices.EnterpriseLibrary.Configuration.ConfigurationManagerSectionHandler, Microsoft.Practices.EnterpriseLibrary.Configuration" />
        <section name="exceptionManagement" type="Microsoft.ApplicationBlocks.ExceptionManagement.ExceptionManagerSectionHandler,
                   Microsoft.ApplicationBlocks.ExceptionManagement"/>
        <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler,log4net" />
    </configSections>
    <enterpriselibrary.configurationSettings xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" defaultSection="" applicationName="Application" xmlns="http://www.microsoft.com/practices/enterpriselibrary/08-31-2004/configuration">
    <configurationSections>
        <configurationSection name="dataConfiguration" encrypt="false">
        <storageProvider xsi:type="XmlFileStorageProviderData" name="XML File Storage Provider" path="dataConfiguration.config" />
        <dataTransformer xsi:type="XmlSerializerTransformerData" name="Xml Serializer Transformer">
            <includeTypes />
        </dataTransformer>
    </configurationSection>
    </configurationSections>
    <keyAlgorithmStorageProvider xsi:nil="true" />
    </enterpriselibrary.configurationSettings>    
</configuration>