public bool FileExists(string localFilepath)
{
/* IMPORTANT
* BEFORE CHANGING OR REFACTORING THIS METHOD, YOU MUST READ THIS NOTICE.
*
* The code below sounds confusing, but there is a reason to be like that.
* The first issue is that the System.IO.File.Exists and Directory.Exists behavior (see Remarks Session in http://msdn.microsoft.com/en-us/library/system.io.file.exists.aspx).
* If an error such as "Acess Denied" or "Invalid Path" occurs during those methods calling,
* .NET API will return FALSE instead of throwing an exception. Thus, when the return is false,
* maybe the file or directory exists, but some error occurred.
* The best way to find out if a file or directory exists is trying to open them. The methods
* that open a file (or directory) will throw an exception if it does not exist.
*
* Now, we have a second issue:
* To do the above, it is necessary that the administrative share on the remote machine is enabled.
* It´s very common that is not enabled.
* The solution to this issue is to make another attempt in order to check file (or directory) existence.
* You can make that through a WMI query.
*
* So, we have three ways to check File Existence. Why not use only WMI ?
* Because, we have a third issue: performance.
* In some scenarios, this WMI Query can be really slow.
* OK, but why the code below still using File.Exists and Directory.Exists methods?
* When those methods return TRUE, we can safely say that file (or directory) really exists.
* Besides, those methods are very fast. Hence, we can stop the method if one of those methods return TRUE.
*/
try
{
var windowsConnectionProvider = new StraightNetworkConnectionProvider();
var adminShareFilePath = GetAdministrativeSharePathFromLocalFilepath(TargetInfo.GetAddress(), localFilepath);
try
{
// To use Administrative Share resource, we need open a straight connection to remote machine.
windowsConnectionProvider.Connect(TargetInfo);
try
{
// If one of these methods return TRUE, we can return this result.
if (System.IO.File.Exists(adminShareFilePath) || System.IO.Directory.Exists(adminShareFilePath))
return true;
// If both methods above return FALSE, we CAN NOT rely on in this.
try
{
// So, we will try to open the file...
System.IO.File.Open(adminShareFilePath, FileMode.Open);
// If we could open it, the file exists.
return true;
}
catch (FileNotFoundException)
{
// obviously we can return FALSE if File.Open thrown FileNotFoundException.
return false;
}
}
catch (Exception)
{
try
{
// If any else Exception was thrown, maybe the passed path is a directory...
// So, we will try to open it.
System.IO.Directory.EnumerateFiles(adminShareFilePath, "*");
return true;
}
catch(FileNotFoundException)
{
return false;
}
}
}
finally
{
windowsConnectionProvider.Disconnect();
}
}
catch (Exception)
{
// At last, if it was not possible to check file (or directory) existence due to any error,
// we will try to find this information out through WMI.
var wmiParametersForFileSearching = this.CreateWmiParameters(localFilepath);
var wqlForFileSearching = new WQLBuilder().WithWmiClass("CIM_LogicalFile").AddParameters(wmiParametersForFileSearching).Build();
var wmiQueryResult = this.WmiDataProvider.ExecuteWQL(wqlForFileSearching);
return ((wmiQueryResult != null) && (wmiQueryResult.Count() > 0));
}
}
public bool FileExists(string localFilepath)
{
/* IMPORTANT
* BEFORE CHANGING OR REFACTORING THIS METHOD, YOU MUST READ THIS NOTICE.
*
* The code below sounds confusing, but there is a reason to be like that.
* The first issue is that the System.IO.File.Exists and Directory.Exists behavior (see Remarks Session in http://msdn.microsoft.com/en-us/library/system.io.file.exists.aspx).
* If an error such as "Acess Denied" or "Invalid Path" occurs during those methods calling,
* .NET API will return FALSE instead of throwing an exception. Thus, when the return is false,
* maybe the file or directory exists, but some error occurred.
* The best way to find out if a file or directory exists is trying to open them. The methods
* that open a file (or directory) will throw an exception if it does not exist.
*
* Now, we have a second issue:
* To do the above, it is necessary that the administrative share on the remote machine is enabled.
* It´s very common that is not enabled.
* The solution to this issue is to make another attempt in order to check file (or directory) existence.
* You can make that through a WMI query.
*
* So, we have three ways to check File Existence. Why not use only WMI ?
* Because, we have a third issue: performance.
* In some scenarios, this WMI Query can be really slow.
* OK, but why the code below still using File.Exists and Directory.Exists methods?
* When those methods return TRUE, we can safely say that file (or directory) really exists.
* Besides, those methods are very fast. Hence, we can stop the method if one of those methods return TRUE.
*/
try
{
var windowsConnectionProvider = new StraightNetworkConnectionProvider();
var adminShareFilePath = GetAdministrativeSharePathFromLocalFilepath(TargetInfo.GetAddress(), localFilepath);
try
{
// To use Administrative Share resource, we need open a straight connection to remote machine.
windowsConnectionProvider.Connect(TargetInfo);
try
{
// If one of these methods return TRUE, we can return this result.
if (System.IO.File.Exists(adminShareFilePath) || System.IO.Directory.Exists(adminShareFilePath))
{
return(true);
}
// If both methods above return FALSE, we CAN NOT rely on in this.
try
{
// So, we will try to open the file...
System.IO.File.Open(adminShareFilePath, FileMode.Open);
// If we could open it, the file exists.
return(true);
}
catch (FileNotFoundException)
{
// obviously we can return FALSE if File.Open thrown FileNotFoundException.
return(false);
}
}
catch (Exception)
{
try
{
// If any else Exception was thrown, maybe the passed path is a directory...
// So, we will try to open it.
System.IO.Directory.EnumerateFiles(adminShareFilePath, "*");
return(true);
}
catch (FileNotFoundException)
{
return(false);
}
}
}
finally
{
windowsConnectionProvider.Disconnect();
}
}
catch (Exception)
{
// At last, if it was not possible to check file (or directory) existence due to any error,
// we will try to find this information out through WMI.
var wmiParametersForFileSearching = this.CreateWmiParameters(localFilepath);
var wqlForFileSearching = new WQLBuilder().WithWmiClass("CIM_LogicalFile").AddParameters(wmiParametersForFileSearching).Build();
var wmiQueryResult = this.WmiDataProvider.ExecuteWQL(wqlForFileSearching);
return((wmiQueryResult != null) && (wmiQueryResult.Count() > 0));
}
}
