WPF FAQ
Questions and answers in this FAQ have been collected from newsgroup posts, various mailing lists and the employees of Syncfusion.

18. Files

 FAQ Home
   18.1 Are there ways to parse text files with Regular Expressions?
   18.2 How to remove a Key From an INI File?
   18.3 How to create a folder in ASP.NET?
   18.4 What is the best way to rename a file on the webserver in code?
   18.5 How to delete a file from the server?
   18.6 How to find the date and time the specified file or directory was last written to?
   18.7 How to get the File information using ASP.NET?
   18.8 How to create a .csv file that grabs the data from the database?
   18.9 How to read text file in ASP.NET?
   18.10 How to read specific characters from a text file?
   18.11 How to check files exist in a particular directory?
   18.12 How to read a html file in ASP.NET?
   18.13 How can I to get the path to the system area that holds temporary files?
   18.14 How to show the ASP.NET code to the users?
   18.15 How to save a file in the client machine?
   18.16 How to get the physical path of a file?
   18.17 How to get the current filename?
   18.18 How to Upload files in ASP.NET?
   18.19 What is a MemoryStream and how to use MemoryStream in ASP.NET?
   18.20 How to detect if the string indicating a file-system resource is a file or directory?



18.1 Are there ways to parse text files with Regular Expressions?

You can use regular expressions to parse delimited text, for example, very easily. Here is an article from ftp online: Parse Text Files With Regular Expressions that discusses this in more detail.


18.2 How to remove a Key From an INI File?

Here is an article from ftp online: Remove a Key From an INI File that describes how this can be done using the native WritePrivateProfileString and GetPrivateProfileString methods.

18.3 How to create a folder in ASP.NET?

Use System.IO namespace
VB.NET


Dim path As String = ""
try
     ' Determine whether the directory exists.
     If Directory.Exists(path) Then
          Response.Write("That path exists already.")
          Return
     End If
     ' Try to create the directory.
     Dim di As DirectoryInfo = Directory.CreateDirectory(path)
     Response.Write(("Directory create successfully at " + Directory.GetCreationTime(path)))
catch ex as Exception
     Response.Write (ex.Message )
end try


C#


string path = @"c:\MyDir";
try
{
     // Determine whether the directory exists.
     if (Directory.Exists(path))
     {
          Response.Write ("That path exists already.");
          return;
     }
     // Try to create the directory.
     DirectoryInfo di = Directory.CreateDirectory(path);
     Response.Write("Directory create successfully at " + Directory.GetCreationTime(path));
}
catch(Exception ex)
{
     Response.Write (ex.Message );
}



18.4 What is the best way to rename a file on the webserver in code?

Use namespace System.IO

VB.NET


File.Move("C:\Dir1\SomeFile.txt", "C:\Dir1\RenamedFileName.txt")


C#


File.Move(@"C:\Dir1\SomeFile.txt", @"C:\Dir1\RenamedFileName.txt")


Refer

Note: In a Web application, the code is running in the context of the machine\ASPNET account, which has limited privileges. If the error you are getting pertains to permissions, you might need to grant to the machine\ASPNET account the rights to create and delete files in the directory where you're working. Note that this could be a security issue.


18.5 How to delete a file from the server?

VB.NET


System.IO.File.Delete(Server.MapPath("wnew.txt"))


C#


System.IO.File.Delete(Server.MapPath("wnew.txt"))


Make sure that you have permissions to delete a file.

18.6 How to find the date and time the specified file or directory was last written to?

Use namespace System.IO
VB.NET


dim path as string = Server.MapPath("page1.aspx")
Response.Write ( File.GetLastWriteTime(path))


C#


string path =Server.MapPath("page1.aspx");
Response.Write ( File.GetLastWriteTime(path));



18.7 How to get the File information using ASP.NET?

Use the namepsace System.IO
VB.NET


Dim fPath As String = Server.MapPath("orders.xml")
Dim fInfo As New FileInfo(fPath)
Dim strFileInfo As String
If fInfo.Exists Then
     strFileInfo = "Name: " + fInfo.Name + "<br />"
     strFileInfo += "Location: " + fInfo.FullName + "<br />"
     strFileInfo += "Created on: " + fInfo.CreationTime + "<br />"
     strFileInfo += "Extension: " + fInfo.Extension
Else
     strFileInfo = "The file <b>" + fPath + "</b> was not found."
End If
Response.Write(strFileInfo)


C#


string fPath = Server.MapPath("orders.xml");
FileInfo fInfo = new FileInfo(fPath);     
string strFileInfo ;
if(fInfo.Exists)
{
     strFileInfo = "Name: " + fInfo.Name + "<br />";
     strFileInfo += "Location: " + fInfo.FullName + "<br />";
     strFileInfo += "Created on: " + fInfo.CreationTime + "<br />";
     strFileInfo += "Extension: " + fInfo.Extension;
}
else
{
     strFileInfo = "The file <b>" + fPath + "</b> was not found.";
}     
Response.Write (strFileInfo);



18.8 How to create a .csv file that grabs the data from the database?


<asp:Button id="Button1" runat="server" Text="Button"></asp:Button>


VB.NET


Dim cn As SqlConnection
Dim cmd As SqlCommand
Dim filename As String
Dim dr As SqlDataReader
Dim i As Integer
Dim sb As System.Text.StringBuilder

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
     cn = New SqlConnection("server=localhost;uid=sa;pwd=;database=northwind")
     filename = "products.csv"
     cmd = New SqlCommand("select * from products ", cn)
     cmd.Connection.Open()
     dr = cmd.ExecuteReader(CommandBehavior.CloseConnection)
     sb = New System.Text.StringBuilder

     'For field Names
     For i = 0 To dr.FieldCount - 1
          If i < (dr.FieldCount - 1) Then
          sb.Append(Chr(34) & dr.GetName(i) & _
               Chr(34) & ",")
          Else
          sb.Append(Chr(34) & dr.GetName(i) & _
               Chr(34) & vbCrLf)
          End If
     Next

     'For field Values
     While dr.Read()
          For i = 0 To dr.FieldCount - 1
          If i < (dr.FieldCount - 1) Then
               sb.Append(Chr(34) & _
                    dr.GetValue(i).ToString & Chr(34) & ",")
          Else
               sb.Append(Chr(34) & _
                    dr.GetValue(i).ToString & Chr(34) & vbCrLf)
          End If
          Next
     End While
     dr.Close()
     cn.Close()
     Response.ContentType = "Application/x-msexcel"
     Response.AddHeader _
          ("content-disposition", "attachment; filename=""" & _
               filename & """")
     'Write the file directly to the HTTP output stream.
     Response.Write(sb.ToString)
     Response.End()
End Sub


C#


SqlConnection cn ;
SqlCommand cmd ;
string filename ;
SqlDataReader dr ;
System.Text.StringBuilder sb ;

private void Button1_Click(object sender, System.EventArgs e)
{
     cn = new SqlConnection("server=localhost;uid=sa;pwd=;database=northwind");
     filename = "products.csv";
     cmd = new SqlCommand("select * from products ", cn);
     cmd.Connection.Open();
     dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
     sb = new System.Text.StringBuilder();

     //For field Names
     for(int i = 0 ;i<= dr.FieldCount - 1;i++)
     {
          if( i < (dr.FieldCount - 1) )
          {
               sb.Append("\t" + dr.GetName(i) + "\t" + ",");
          }
          else
          {
               sb.Append("\t" + dr.GetName(i) + "\t" + "\n");
          }
     }

     //For field Values
     while( dr.Read())
     {
          for(int i = 0 ;i<= dr.FieldCount - 1;i++)
           {
                if( i < (dr.FieldCount - 1) )
                {
                     sb.Append("\t" + dr.GetValue(i) + "\t" + ",");
                }
                else
                {
                     sb.Append("\t" + dr.GetValue(i) + "\t" + "\n");
                }
           }
     }
      dr.Close();
      cn.Close();
      Response.ContentType = "Application/x-msexcel";
      Response.AddHeader ("content-disposition", "attachment; filename=" + filename ) ;
     
     //Write the file directly to the HTTP output stream.
     Response.Write(sb.ToString());
     Response.End();
}



18.9 How to read text file in ASP.NET?

Use namespace System.IO
VB.NET


Dim sr As StreamReader
sr = File.OpenText(Server.MapPath("1.txt"))
Dim strContents As String = sr.ReadToEnd()
'To display normal raw contents
Response.Write(strContents)

'To handle Carriage returns
Response.Write(strContents.Replace(vbCrLf, "<br>"))

sr.Close()


C#


StreamReader sr = File.OpenText(Server.MapPath("1.txt"));
string strContents = sr.ReadToEnd();
//To display normal raw contents
Response.Write(strContents);

//To handle Carriage returns
Response.Write(strContents.Replace("\n" , "<br>"));

sr.Close();



18.10 How to read specific characters from a text file?

Use namespace System.IO
VB.NET


Dim fs As New System.IO.FileStream(Server.MapPath("1.txt"), IO.FileMode.Open)
Dim buffer(5) As Byte ' 5=> number of characters to be read
fs.Read(buffer, 0, 5)
fs.Close()
Dim filechars() As Char = System.Text.Encoding.ASCII.GetChars(buffer)
Dim filestring As String = New String(filechars)
Response.Write(filestring)


C#


FileStream fs =new FileStream(Server.MapPath("1.txt"), FileMode.Open);
Byte[] buffer= new byte [5] ; //5 => Number of characters to be read
fs.Read(buffer, 0, 5);
fs.Close();
Char[] filechars = System.Text.Encoding.ASCII.GetChars(buffer);
string filestring = new String(filechars);
Response.Write(filestring);



18.11 How to check files exist in a particular directory?

Try to use "System.IO.File.Exists("path")". path is the physical file path and it will return you a boolean value.

18.12 How to read a html file in ASP.NET?

Use namespace System.IO
VB.NET


Dim file As String = Server.MapPath("temp.html")
Dim sr As StreamReader
Dim fi As New FileInfo(file)
Dim input As String = "<pre>"
If File.Exists(file) Then
sr = File.OpenText(file)
input += Server.HtmlEncode(sr.ReadToEnd())
sr.Close()
End If
input += "</pre>"
Me.Label1.Text = input


C#


string file = Server.MapPath ("temp.html");
StreamReader sr;
FileInfo fi = new FileInfo(file);
string input = "<pre>";
if(File.Exists(file))
{
     sr = File.OpenText(file);
     input += Server.HtmlEncode(sr.ReadToEnd());
     sr.Close();
}
input += "</pre>";
this.Label1.Text = input;



18.13 How can I to get the path to the system area that holds temporary files?

Use System.IO namespace
VB.NET


Dim filePath As String = Path.GetTempPath()
Dim fileName As String = Path.GetTempFileName()
Response.Write((filePath + "
"))
Response.Write(fileName)


C#


string filePath =Path.GetTempPath ();
string fileName = Path.GetTempFileName();
Response.Write (filePath + "
" );
Response.Write (fileName );



18.14 How to show the ASP.NET code to the users?

Use namespace

  • System.IO
  • System.Text

VB.NET


Protected Function GetCode(filename As String) As String
     Dim sr As New StreamReader(filename)
     Dim sb As New StringBuilder()
     sb.Append("<code><pre>")
     sb.Append(sr.ReadToEnd())
     sb.Append("</pre></code>")
     sr.Close()
     Return sb.ToString()
     sb = Nothing
     sr = Nothing
End Function 'GetCode

Private Sub Button1_Click(sender As Object, e As System.EventArgs)
     Response.Write(GetCode((Server.MapPath("WebForm1.aspx") + ".vb")))
End Sub 'Button1_Click


C#


protected string GetCode(string filename)
{
     StreamReader sr =new StreamReader(filename );
     StringBuilder sb =new StringBuilder();
     sb.Append("<code><pre>");
     sb.Append(sr.ReadToEnd());
     sb.Append("</pre></code>");
     sr.Close();
     return sb.ToString();
     sb = null;
     sr = null;
}
private void Button1_Click(object sender, System.EventArgs e)
{
     Response.Write (GetCode(Server.MapPath ("WebForm1.aspx") + ".cs"));
}



18.15 How to save a file in the client machine?

The browser will not allow you to save a file directly to a client machine. You could however do a Response.Redirect("http://server/filename"); which would send the file back to the browser, at which point the user would be prompted to save / open the file.

18.16 How to get the physical path of a file?

Use Request.Path

18.17 How to get the current filename?

VB.NET


Response.Write (Path.GetFileName(Request.PhysicalPath))


C#


Response.Write (Path.GetFileName(Request.PhysicalPath));



18.18 How to Upload files in ASP.NET?

Take a look at following articles


18.19 What is a MemoryStream and how to use MemoryStream in ASP.NET?

The MemoryStream class creates streams that use memory as storage instead of a disk or a network connection. MemoryStream encapsulates data stored as an unsigned byte array that is initialized upon creation of a MemoryStream object, or the array can be created as empty. The encapsulated data is directly accessible in memory. Memory streams can reduce the need for temporary buffers and files in an application.
For more details refer


18.20 How to detect if the string indicating a file-system resource is a file or directory?

VB.NET


Dim path As String = Server.MapPath("webform1.aspx")
' Put user code to initialize the page here
If(File.GetAttributes(path) And FileAttributes.Directory) = FileAttributes.Directory Then
     Response.Write("Its a directory")
Else
     Response.Write("Its a file")
End If


C#


string path =Server.MapPath ("webform1.aspx");
if ((File.GetAttributes(path) & FileAttributes.Directory) ==FileAttributes.Directory)
{
     Response.Write ("Its a directory");
}
else
{
     Response.Write ("Its a file");
}


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