c#命名空间已经包含了继承类的定义，所以如何添加构造函数

我正在小心翼翼地进入WCF，试图遵循教程并将我的ASMX项目转换为新的WCF项目，我偶然发现了一个关于在WCF中编写构造函数的奥秘。

我的ASMX webservice允许我有一个构造函数(参见:同名，无返回值):

namespace sdkTrimFileServiceASMX
{
public class FileService : System.Web.Services.WebService
{
    Database db;
    string g_EventSource = "CBMI-TrimBroker";
    string g_EventLog = "Application";
    public FileService()
    {
        try
        {
            if (!EventLog.SourceExists(g_EventSource))
                EventLog.CreateEventSource(g_EventSource, g_EventLog);
        }
        catch (InvalidOperationException e)
        {
            e.ToString();
        }
    }

我尝试将其转换为WCF服务应用程序时，编译器报错:

The namespace 'sdkTRIMFileServiceWCF' already contains a definition for 'FileService'   

下面是WCF代码(开始代码段):

namespace sdkTRIMFileServiceWCF
{
[ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)]
public class FileService : IFileService                             // err msg points to this line
{
    Database db;
    string g_EventSource = "CBMI-TrimBroker";
    string g_EventLog = "Application";
    public FileService()
    {
        try
        {
            if (!EventLog.SourceExists(g_EventSource))
                EventLog.CreateEventSource(g_EventSource, g_EventLog);
        }
        catch (InvalidOperationException e)
        {
            e.ToString();
        }
    }