Writing Filestream to file and reading bfile

Question

I have a web service that checks a dictionary to find out if a file exists, and then if it exists, it reads the file, otherwise it saves the file. This is from a web application. Interestingly, the best way to do this is because I sometimes get a FileNotFoundException if the same file is available at the same time. Here are the relevant parts of the code:

String signature;
signature = "FILE," + value1 + "," + value2 + "," + value3 + "," + value4;     // this is going to be the filename

string result;            
MultipleRecordset mrSummary = new MultipleRecordset();  // MultipleRecordset is an object that retrieves data from a sql server database

if (mrSummary.existsFile(signature))
{                
    result = mrSummary.retrieveFile(signature);                
}
else
{                
    result = mrSummary.getMultipleRecordsets(System.Configuration.ConfigurationManager.ConnectionStrings["MyConnectionString"].ConnectionString.ToString(), value1, value2, value3, value4);
    mrSummary.saveFile(signature, result);
}

Here is the code to find out if a file exists:

private static Dictionary<String, bool> dict = new Dictionary<String, bool>();

public bool existsFile(string signature)
{                       
    if (dict.ContainsKey(signature))
    {
        return true;
    }
    else
    {
        return false;
    }                                
}

Here is what I use to extract if it already exists:

try
{                               

    byte[] buffer;
    FileStream fileStream = new FileStream(@System.Configuration.ConfigurationManager.AppSettings["CACHEPATH"] + filename, FileMode.Open, FileAccess.Read, FileShare.Read);
      try
      {
        int length = 0x8000;  // get file length
        buffer = new byte[length];            // create buffer
        int count;                            // actual number of bytes read
        JSONstring = "";
        while ((count = fileStream.Read(buffer, 0, length)) > 0)
        {
            JSONstring += System.Text.ASCIIEncoding.ASCII.GetString(buffer, 0, count);
        }
      }
      finally
      {
        fileStream.Close();
      }
}
catch (Exception e)
{

    JSONstring = "{\"error\":\"" + e.ToString() + "\"}";                
}

If the file did not exist before, it saves the JSON to the file:

try 
{                
    if (dict.ContainsKey(filename) == false)
    {
        dict.Add(filename, true);
    }
    else
    {
        this.retrieveFile(filename, ipaddress);
    }

}
catch
{


}


try
{
    TextWriter tw = new StreamWriter(@System.Configuration.ConfigurationManager.AppSettings["CACHEPATH"] + filename);
    tw.WriteLine(JSONstring);
    tw.Close();
}
catch { 

}

Here are the details of the exception that I sometimes get from executing the above code:

System.IO.FileNotFoundException: Could not find file 'E:\inetpub\wwwroot\cache\FILE,36,36.25,14.5,14.75'.
File name: 'E:\inetpub\wwwroot\cache\FILE,36,36.25,14.5,14.75'
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share)
   at com.myname.business.MultipleRecordset.retrieveFile(String filename, String ipaddress)

Answer 1

FileNotFoundException, , . , .

: ( ). , Dictionary<string, object> . .

, , , Monitor.Enter Monitor.Exit. :

static HashSet<string> files = new HashSet<string>();
static object syncRoot = new object();

void Whatever(string filename, string ipaddress)
{
    bool fileFound;

    lock (syncRoot)
    {
        fileFound = files.Contains(filename);
        if (!fileFound)
        {
            files.Add(filename);
            // Code to write file here
        }
    }

    if (fileFound)
    {
        retrieveFile(filename, ipaddress);
    }
}

, , , . , .

HashSet , , , , .

Answer 2

.

FileNotFoundException

  FileStream fileStream = new FileStream(System.Configuration.ConfigurationManager.AppSettings["CACHEPATH"] + filename, FileMode.Open, FileAccess.Read, FileShare.Read);  

.

dict.Add(filename, true);

TextWriter tw = new StreamWriter(@System.Configuration.ConfigurationManager.AppSettings["CACHEPATH"] + filename); 
tw.WriteLine(JSONstring); 
tw.Close(); 

- .

public bool existsFile(string signature)       
{                              
    if (dict.ContainsKey(signature))       
    {       
        return true;       
    }       
    else       
    {       
        return false;       
    }                                       
}