Could not load file or assembly ‘[NAME]‘ or one of its dependencies. An attempt was made to load a program with an incorrect format.

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

It seems that by specifying the Target Platform of 64-bit in this case, a 32-bit application was causing a collision. Below are the steps that I was able to follow in order to clear up the issue:

Steps

1. Open the project file for editing in Visual Studio.
1. Right-click on the project file in Solution Explorer
2. Select ‘Edit Project File’
2. Remove the PlatformTarget element from all configuration property groups.

<PropertyGroup Condition=” ‘$(Configuration)|$(Platform)’ == ‘Debug|AnyCPU’ “>
<DebugSymbols></DebugSymbols>
<DebugType></DebugType>
<Optimize></Optimize>
<OutputPath></OutputPath>
<DefineConstants></DefineConstants>
<ErrorReport></ErrorReport>
<WarningLevel></WarningLevel>
<PlatformTarget>x64</PlatformTarget>
</PropertyGroup>

The email service that I’m calling into accepts the ToAddress as a string[] array of email addresses (which it then probably converts to System.Net.Mail.MailAddresses). My ToAddress was being read from a config file where the entry read something like:  “email@domain.com;email2@domain.com“. I was seeing the error because the config entry was not being split out into a string[] array properly, and SmtpClient apparently doesn’t like stray characters (“;”) in its email addresses. Quick solution:

// Read recipient from config file
var recipient = ConfigurationManager.AppSettings["CONFIG_KEY"];

// Make sure addresses are all separated by the same delimiting character
recipient = recipient.Replace(“,”, “;”);

// Split the recipient string by the delimiting character and build a string[] array of recipients
var toAddresses = recipient.Split(new char[] { ‘;’ }, StringSplitOptions.RemoveEmptyEntries);

Note:
System.Net.Mail.MailMessage’s “To” property is a collection of MailAddresses. If you need to populate MailAddress objects yourself you can do a few things differently:

// Continue from the above string[] array method
var mailAddresses = new MailAddressCollection();

// Use each address to create a new MailAddress and add to the MailAddressCollection
toAddresses.ToList().ForEach(address =>
{
mailAddresses.Add(new MailAddress(address));
}

OR

// Make sure addresses are all separated by a comma
recipient = recipient.Replace(“;”, “,”);

// MailAddressCollection has a constructor that accepts a comma-delimited list of email addresses
var mailAddresses = new MailAddressCollection() { recipient };