SPWebConfigModification adding child nodes in undesired order

Question

I have some code that uses SPWebConfigModification to add a couple of nodes to the system.webServer/modules section. What I want to do is add a <remove name="MyModule" /> and then an <add name="MyModule" type="[type full assembly path]">.

No matter what I seem to do though, the web.config always ends up with the <add ../> before the <remove ../>. This is obviously incorrect, as the module will be removed after it is added. What I want to do is remove it, then add it. Here is what the web.config ends up looking like:

<configuration>
    <system.webServer>
        <modules runAllManagedModulesForAllRequests="true">
            <add name="MyModule" type="[type full assembly path]" />
            <remove name="MyModule" />
        </modules>
    </system.webServer>
</configuration>

Here is what I want it to look like:

<configuration>
    <system.webServer>
        <modules runAllManagedModulesForAllRequests="true">
            <remove name="MyModule" />
            <add name="MyModule" type="[type full assembly path]" />
        </modules>
    </system.webServer>
</configuration>

..and here is the code, which gets executed during SPFeatureReceiver.FeatureInstalled:

SPSecurity.RunWithElevatedPrivileges(delegate
{
    SPWebService spWebService = SPWebService.ContentService;

    var moduleModification = new SPWebConfigModification
    {
        Path = "configuration/system.webServer/modules",
        Name = "remove[@name='MyModule']",
        Sequence = 0,
        Owner = "Sample",
        Type = SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode,
        Value = "<remove name='MyModule' />",
    };
    spWebService.WebConfigModifications.Add(moduleModification);
    spWebService.Update();
    spWebService.ApplyWebConfigModifications();

    moduleModification = new SPWebConfigModification
    {
        Path = "configuration/system.webServer/modules",
        Name = "add[@name='MyModule'][@type='[type full assembly path]']",
        Sequence = 1000,
        Owner = "Sample",
        Type = SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode,
        Value = "<add name='MyModule' type='type full assembly path' />",
    };
    spWebService.WebConfigModifications.Add(moduleModification);

    spWebService.Update();
    spWebService.ApplyWebConfigModifications();
});

... I know I am supposed to be able to make both of these changes before calling Update and ApplyWebConfigModifications, but just have this code in here this way because I can't figure out why it is putting the add above the remove. Why is it doing it this way? Is it trying to alphabetize the nodes? How can I specify the order?

Answer 1

Yes, the nodes are being alphabetically sorted and the Sequence property only applies when the Name property is exactly the same. To fix, use a little XPath trickery to get your nodes to sort in the correct order (first modules[1=1] then modules[2=2]):

SPSecurity.RunWithElevatedPrivileges(delegate
{
    SPWebService spWebService = SPWebService.ContentService;

    var moduleModification = new SPWebConfigModification
    {
        Path = "configuration/system.webServer",
        Name = "modules[1=1]/remove[@name='MyModule']",
        Sequence = 0,
        Owner = "Sample",
        Type = SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode,
        Value = "<remove name='MyModule' />",
    };
    spWebService.WebConfigModifications.Add(moduleModification);

    moduleModification = new SPWebConfigModification
    {
        Path = "configuration/system.webServer",
        Name = "modules[2=2]/add[@name='MyModule'][@type='[type full assembly path]']",
        Sequence = 1000,
        Owner = "Sample",
        Type = SPWebConfigModification.SPWebConfigModificationType.EnsureChildNode,
        Value = "<add name='MyModule' type='type full assembly path' />",
    };
    spWebService.WebConfigModifications.Add(moduleModification);

    spWebService.Update();
    spWebService.ApplyWebConfigModifications();
});

Also, you might want to double check what happens when you call ApplyWebConfigModifications to make sure your changes are propagated across the farm. Since you're calling it on an SPWebService I think it is OK but we always use the following:

webApp.Farm.Services.GetValue<SPWebService>().ApplyWebConfigModifications();

Sources:

• Master the order of WebConfigModifications
• How To: Modify the web.config file in SharePoint using SPWebConfigModification