How to read and update external web.config by a c# Windows forms application

Question

I am building a c# Windows application to maintain a WEB application - special to create and update values in a web.config file. I have tried many suggestions here, but all of them are simply describing to read and write config files from inside the application. Part of the web.config:

- 
 <configuration>
    <system.web>
        <customErrors mode="Off"/>

        <compilation debug="true" targetFramework="4.0" />
        <globalization culture="" enableClientBasedCulture="true" uiCulture="" />

        <pages controlRenderingCompatibilityVersion="3.5" clientIDMode="AutoID" />
    </system.web>
    <appSettings>
        <add key="DocPath" value="~/serverdocs/docs" />

        <add key="TextForLabel1" value="This is some text"/>
..

I tried to read the file - special all keys from appSettings -like

    var xmlDoc = new XmlDocument();
        xmlDoc.Load(FName); // name and path from web.config file

And then to read all nodes like :

            foreach (XmlNodeList xmlnodes in xmlDoc.SelectNodes("configuration/appSettings"))
            {
                foreach ( XmlNode node in xmlnodes)
                {
                string MyKey = node.Name;
                string MyVal = node.Value;
                }

            }  

But there are always errors like The object of type "System.Xml.XmlDeclaration" cannot be converted to Type "System.Xml.XmlNodeList". Or the items are simply not found depending on how I write the select value. I have tried '//configuration' and 'configuration/appSettings' and others.

Sometimes I am probably blind reading my own code and detecting the error - sorry - any suggestion is welcome.

Answer 1

Although the configuration files are XML they can be difficult to enumerate and locate in an XmlDocument.

Instead, you can actually use a WebConfigurationManager which is specifically designed to read and write web.config files:

Configuration cfg = WebConfigurationManager.OpenWebConfiguration("YOUR_WEB_CONFIG");

Once you have the data in the Configuration object, you can enumerate the sections and values of the configuration file.

You will need to add a reference to both System.Configuration and System.Web in order to utilise the above.

EDIT

Following Willhelm's comment that he was unable to open the web.config from the physical path of the file, the following snippet (stolen directly from this answer) can be used to load the file:

public static Configuration OpenConfigFile(string configPath)
{
    var configFile = new FileInfo(configPath);
    var vdm = new VirtualDirectoryMapping(configFile.DirectoryName, true, configFile.Name);
    var wcfm = new WebConfigurationFileMap();
    wcfm.VirtualDirectories.Add("/", vdm);
    return WebConfigurationManager.OpenMappedWebConfiguration(wcfm, "/");
}

To use:

Configuration cfg = OpenConfigFile(@"YOUR_WEB_CONFIG");

Answer 2

to read it:

   var xmlDoc = new XmlDocument();
    xmlDoc.Load(FName);
    DataTable DTConfig = new DataTable();
    DTConfig.Columns.Add("Key", typeof(string));
    DTConfig.Columns.Add("Value", typeof(string));
    DTConfig.Columns.Add("OldValue", typeof(string));
    try
    {
        foreach (XmlElement xmlElement in xmlDoc.SelectNodes("configuration/appSettings"))
        {
            foreach (XmlNode node in xmlElement)
            {
                if (node.Attributes != null && node.Attributes.Count > 1)
                {
                    string MyKey = "";
                    string MyVal = "";
                    if (node.Attributes[0].Value != null)
                    {
                        MyKey = node.Attributes[0].Value;
                    }
                    if (node.Attributes[1].Value != null)
                    {
                        MyVal = node.Attributes[1].Value;
                    }
                    DataRow DR = DTConfig.NewRow();
                    DR["Key"] = MyKey;
                    DR["Value"] = MyVal;
                    DR["OldValue"] = MyVal;
                    if (MyKey != "")
                    {
                        DTConfig.Rows.Add(DR);
                    }
                }
            }
        }
    }
    catch (Exception ex)
    {
        Debug.Print(ex.Message);
    }
    TxtFname.Text = FName;
    DGConfig.DataSource = DTConfig;
    return true;

The datatable is bound to a datagridview - thats all

Answer 3

I had a similar problem and went down the same road you did, trying to walk the XML tree to find the node I needed to change. It was a key/value pair that defined a the URI for a web service connection. The default URI pointed to localhost, e.g.:

    <add key="ProcessorService" value="https://localhost/Processor/ProcessorService.asmx" />

...and I needed to point it to the server upon which the service actually ran, which depends on which box it runs on (Dev, QA, UAT, Prod, etc.)

I pulled my hair out trying to walk that silly tree, and there were eight different web configs that needed similar modifications for each server upon which the sites were installed. Each web.config was structured differently, of course.

I solved it with a regex in the PowerShell installation script for the sites, here's a snippet:

(Get-Content $webConfig -Encoding UTF8) | `
    ForEach-Object {$_ -replace 'localhost', "$dnsName" } | `
    Set-Content $webConfig

I ran the above inside of a loop that went through each web.config file in each directory, made the modification, then saved the file with the Set-Content cmdlet.

I can understand if you have to do this in C#, you could always just open the file as a stream, have a few Regex objects set up, and perform essentially the same operation.

Me? Personally, I hate walking XML unless I'm forced to. You can most certainly do it that way, but if someone comes along and rearranges your web.config file, they'll break your nicely crafted XML walker and you'll be starting all over. This way, as long as what you're changing doesn't change (much) it should work just fine.