Verify if file exists or not in C

Question

I am working on an application  That application should get the resume from the users  so that I need a code to verify whether a file exists or not   I m using ASP NET   C

User · Answer

You could use   System IO File Exists   c  temp test txt

User · Answer

To test whether a file exists in  NET  you can use  System IO File Exists  String

User · Answer

if  File Exists Server MapPath    Images associates     Html DisplayFor modelItem   gt  item AssociateImage                        lt img src    Images associates  Html DisplayFor modelItem   gt  item AssociateImage   gt                   else                    lt h5 gt No image available lt  h5 gt             I did something like this for checking to see if an image existed before displaying it

User · Answer

Try this        string fileName    6d294041-34d1-4c66-a04c-261a6d9aee17 jpeg         string deletePath    images uploads          if   string IsNullOrEmpty fileName                             Append the name of the file to previous image              deletePath    fileName                if  File Exists HttpContext Current Server MapPath deletePath                                     deletevprevious image                 File Delete HttpContext Current Server MapPath deletePath

User · Answer

You can determine whether a specified file exists using the Exists method of the File class in the System IO namespace   bool System IO File Exists string path    You can find the documentation here on MSDN   Example   using System  using System IO   class Test       public static void Main                 string resumeFile     c  ResumesArchive 923823 txt           string newFile     c  ResumesImport newResume txt           if  File Exists resumeFile                         File Copy resumeFile  newFile                     else                       Console WriteLine  Resume file does not exist

User · Answer

You could use   System IO File Exists   c  temp test txt

User · Answer

Simple answer is that you can t - you won t be able to check a for a file on their machine from an ASP website  as to do so would be a dangerous risk for them   You have to give them a file upload control - and there s not much you can do with that control  For security reasons javascript can t really touch it    lt asp FileUpload ID  FileUpload1  runat  server    gt    They then pick a file to upload  and you have to deal with any empty file that they might send up server side

User · Answer

In addition to using File Exists    you might be better off just trying to use the file and catching any exception that is thrown  The file can fail to open because of other things than not existing

User · Answer

Simple answer is that you can t - you won t be able to check a for a file on their machine from an ASP website  as to do so would be a dangerous risk for them   You have to give them a file upload control - and there s not much you can do with that control  For security reasons javascript can t really touch it    lt asp FileUpload ID  FileUpload1  runat  server    gt    They then pick a file to upload  and you have to deal with any empty file that they might send up server side

User · Answer

These answers all assume the file you are checking is on the server side   Unfortunately  there is no cast iron way to ensure that a file exists on the client side  e g  if you are uploading the resume    Sure  you can do it in Javascript but you are still not going to be 100  sure on the server side   The best way to handle this  in my opinion  is to assume that the user will actually select an appropriate file for upload  and then do whatever work you need to do to ensure the uploaded file is what you expect  hint - assume the user is trying to poison your system in every possible way with his her input

User · Answer

In addition to using File Exists    you might be better off just trying to use the file and catching any exception that is thrown  The file can fail to open because of other things than not existing

User · Answer

You wrote asp net - are you looking to upload a file  if so you can use the html       lt input type  file

User · Answer

Simple answer is that you can t - you won t be able to check a for a file on their machine from an ASP website  as to do so would be a dangerous risk for them   You have to give them a file upload control - and there s not much you can do with that control  For security reasons javascript can t really touch it    lt asp FileUpload ID  FileUpload1  runat  server    gt    They then pick a file to upload  and you have to deal with any empty file that they might send up server side

User · Answer

You could use   System IO File Exists   c  temp test txt

User · Answer

Can t comment yet  but I just wanted to disagree clarify with erikkallen     You should not just catch the exception in the situation you ve described   If you KNEW that the file should be there and due to some exceptional case  it wasn t  then it would be acceptable to just attempt to access the file and catch any exception that occurs     In this case  however  you are receiving input from a user and have little reason to believe that the file exists   Here you should always use File Exists     I know it is clich    but you should only use Exceptions for an exceptional event  not as part as the normal flow of your application   It is expensive and makes code more difficult to read follow

User · Answer

You could use   System IO File Exists   c  temp test txt

User · Answer

To test whether a file exists in  NET  you can use  System IO File Exists  String

User · Answer

These answers all assume the file you are checking is on the server side   Unfortunately  there is no cast iron way to ensure that a file exists on the client side  e g  if you are uploading the resume    Sure  you can do it in Javascript but you are still not going to be 100  sure on the server side   The best way to handle this  in my opinion  is to assume that the user will actually select an appropriate file for upload  and then do whatever work you need to do to ensure the uploaded file is what you expect  hint - assume the user is trying to poison your system in every possible way with his her input

User · Answer

You can determine whether a specified file exists using the Exists method of the File class in the System IO namespace   bool System IO File Exists string path    You can find the documentation here on MSDN   Example   using System  using System IO   class Test       public static void Main                 string resumeFile     c  ResumesArchive 923823 txt           string newFile     c  ResumesImport newResume txt           if  File Exists resumeFile                         File Copy resumeFile  newFile                     else                       Console WriteLine  Resume file does not exist

User · Answer

You wrote asp net - are you looking to upload a file  if so you can use the html       lt input type  file

User · Answer

These answers all assume the file you are checking is on the server side   Unfortunately  there is no cast iron way to ensure that a file exists on the client side  e g  if you are uploading the resume    Sure  you can do it in Javascript but you are still not going to be 100  sure on the server side   The best way to handle this  in my opinion  is to assume that the user will actually select an appropriate file for upload  and then do whatever work you need to do to ensure the uploaded file is what you expect  hint - assume the user is trying to poison your system in every possible way with his her input

User · Answer

Simple answer is that you can t - you won t be able to check a for a file on their machine from an ASP website  as to do so would be a dangerous risk for them   You have to give them a file upload control - and there s not much you can do with that control  For security reasons javascript can t really touch it    lt asp FileUpload ID  FileUpload1  runat  server    gt    They then pick a file to upload  and you have to deal with any empty file that they might send up server side

User · Answer

if  File Exists Server MapPath    Images associates     Html DisplayFor modelItem   gt  item AssociateImage                        lt img src    Images associates  Html DisplayFor modelItem   gt  item AssociateImage   gt                   else                    lt h5 gt No image available lt  h5 gt             I did something like this for checking to see if an image existed before displaying it

User · Answer

You wrote asp net - are you looking to upload a file  if so you can use the html       lt input type  file

User · Answer

To test whether a file exists in  NET  you can use  System IO File Exists  String

User · Answer

Try this        string fileName    6d294041-34d1-4c66-a04c-261a6d9aee17 jpeg         string deletePath    images uploads          if   string IsNullOrEmpty fileName                             Append the name of the file to previous image              deletePath    fileName                if  File Exists HttpContext Current Server MapPath deletePath                                     deletevprevious image                 File Delete HttpContext Current Server MapPath deletePath

User · Answer

You can determine whether a specified file exists using the Exists method of the File class in the System IO namespace   bool System IO File Exists string path    You can find the documentation here on MSDN   Example   using System  using System IO   class Test       public static void Main                 string resumeFile     c  ResumesArchive 923823 txt           string newFile     c  ResumesImport newResume txt           if  File Exists resumeFile                         File Copy resumeFile  newFile                     else                       Console WriteLine  Resume file does not exist

User · Answer

In addition to using File Exists    you might be better off just trying to use the file and catching any exception that is thrown  The file can fail to open because of other things than not existing

User · Answer

Can t comment yet  but I just wanted to disagree clarify with erikkallen     You should not just catch the exception in the situation you ve described   If you KNEW that the file should be there and due to some exceptional case  it wasn t  then it would be acceptable to just attempt to access the file and catch any exception that occurs     In this case  however  you are receiving input from a user and have little reason to believe that the file exists   Here you should always use File Exists     I know it is clich    but you should only use Exceptions for an exceptional event  not as part as the normal flow of your application   It is expensive and makes code more difficult to read follow

User · Answer

In addition to using File Exists    you might be better off just trying to use the file and catching any exception that is thrown  The file can fail to open because of other things than not existing

User · Answer

This may help you   try             con Open           if   fileUpload1 PostedFile    null   amp  amp   fileUpload1 PostedFile ContentLength  gt  0                       filename   System IO Path GetFileName fileUpload1 PostedFile FileName              ext   System IO Path GetExtension filename  ToLower               string str    Resumes     filename             saveloc    Server MapPath        str              string   exts       doc     docx     pdf     rtf                for  int i   0  i  lt  exts Length  i                                if  ext    exts i                      fileok   true                          if  fileok                              if  File Exists saveloc                      throw new Exception Label1 Text  File exists                      fileUpload1 PostedFile SaveAs saveloc                  cmd   new SqlCommand  insert into candidate values      candidatename           candidatemail           candidatemobile           filename           str         con                  cmd ExecuteNonQuery                   Label1 Text    Upload Successful                     Label1 ForeColor   System Drawing Color Blue                 con Close                            else                             Label1 Text    Upload not successful                     Label1 ForeColor   System Drawing Color Red                                  catch  Exception ee    Label1 Text   ee Message

User · Answer

You can determine whether a specified file exists using the Exists method of the File class in the System IO namespace   bool System IO File Exists string path    You can find the documentation here on MSDN   Example   using System  using System IO   class Test       public static void Main                 string resumeFile     c  ResumesArchive 923823 txt           string newFile     c  ResumesImport newResume txt           if  File Exists resumeFile                         File Copy resumeFile  newFile                     else                       Console WriteLine  Resume file does not exist

User · Answer

Can t comment yet  but I just wanted to disagree clarify with erikkallen     You should not just catch the exception in the situation you ve described   If you KNEW that the file should be there and due to some exceptional case  it wasn t  then it would be acceptable to just attempt to access the file and catch any exception that occurs     In this case  however  you are receiving input from a user and have little reason to believe that the file exists   Here you should always use File Exists     I know it is clich    but you should only use Exceptions for an exceptional event  not as part as the normal flow of your application   It is expensive and makes code more difficult to read follow

User · Answer

This may help you   try             con Open           if   fileUpload1 PostedFile    null   amp  amp   fileUpload1 PostedFile ContentLength  gt  0                       filename   System IO Path GetFileName fileUpload1 PostedFile FileName              ext   System IO Path GetExtension filename  ToLower               string str    Resumes     filename             saveloc    Server MapPath        str              string   exts       doc     docx     pdf     rtf                for  int i   0  i  lt  exts Length  i                                if  ext    exts i                      fileok   true                          if  fileok                              if  File Exists saveloc                      throw new Exception Label1 Text  File exists                      fileUpload1 PostedFile SaveAs saveloc                  cmd   new SqlCommand  insert into candidate values      candidatename           candidatemail           candidatemobile           filename           str         con                  cmd ExecuteNonQuery                   Label1 Text    Upload Successful                     Label1 ForeColor   System Drawing Color Blue                 con Close                            else                             Label1 Text    Upload not successful                     Label1 ForeColor   System Drawing Color Red                                  catch  Exception ee    Label1 Text   ee Message

User · Answer

I have written this code in vb and its is working fine to check weather a file is exists or not for fileupload control  try it   FOR VB CODE                   If FileUpload1 HasFile   True Then         Dim FileExtension As String   System IO Path GetExtension FileUpload1 FileName           If FileExtension ToLower  lt  gt    jpg  Then             lblMessage ForeColor   System Drawing Color Red             lblMessage Text    Please select  jpg image file to upload          Else             Dim FileSize As Integer   FileUpload1 PostedFile ContentLength              If FileSize  gt  1048576 Then                 lblMessage ForeColor   System Drawing Color Red                 lblMessage Text    File size  1MB  exceeded              Else                 Dim FileName As String   System IO Path GetFileName FileUpload1 FileName                   Dim ServerFileName As String   Server MapPath    Images Folder1     FileName                   If System IO File Exists ServerFileName    False Then                     FileUpload1 SaveAs Server MapPath    Images Folder1      FileUpload1 FileName                      lblMessage ForeColor   System Drawing Color Green                     lblMessage Text    File       FileUpload1 FileName     uploaded successfully                  Else                     lblMessage ForeColor   System Drawing Color Red                     lblMessage Text    File       FileName ToString       already exsist                  End If             End If         End If     Else         lblMessage ForeColor   System Drawing Color Red         lblMessage Text    Please select a file to upload      End If   FOR C  CODE                         if  FileUpload1 HasFile    true        string FileExtension   System IO Path GetExtension FileUpload1 FileName        if  FileExtension ToLower      jpg             lblMessage ForeColor   System Drawing Color Red          lblMessage Text    Please select  jpg image file to upload         else           int FileSize   FileUpload1 PostedFile ContentLength           if  FileSize  gt  1048576                lblMessage ForeColor   System Drawing Color Red              lblMessage Text    File size  1MB  exceeded             else               string FileName   System IO Path GetFileName FileUpload1 FileName                string ServerFileName   Server MapPath    Images Folder1     FileName                if  System IO File Exists ServerFileName     false                    FileUpload1 SaveAs Server MapPath    Images Folder1      FileUpload1 FileName                   lblMessage ForeColor   System Drawing Color Green                  lblMessage Text    File       FileUpload1 FileName     uploaded successfully                 else                   lblMessage ForeColor   System Drawing Color Red                  lblMessage Text    File       FileName ToString       already exsist                                   else       lblMessage ForeColor   System Drawing Color Red      lblMessage Text    Please select a file to upload

User · Answer

To test whether a file exists in  NET  you can use  System IO File Exists  String

User · Answer

These answers all assume the file you are checking is on the server side   Unfortunately  there is no cast iron way to ensure that a file exists on the client side  e g  if you are uploading the resume    Sure  you can do it in Javascript but you are still not going to be 100  sure on the server side   The best way to handle this  in my opinion  is to assume that the user will actually select an appropriate file for upload  and then do whatever work you need to do to ensure the uploaded file is what you expect  hint - assume the user is trying to poison your system in every possible way with his her input

User · Answer

You wrote asp net - are you looking to upload a file  if so you can use the html       lt input type  file

User · Answer

I have written this code in vb and its is working fine to check weather a file is exists or not for fileupload control  try it   FOR VB CODE                   If FileUpload1 HasFile   True Then         Dim FileExtension As String   System IO Path GetExtension FileUpload1 FileName           If FileExtension ToLower  lt  gt    jpg  Then             lblMessage ForeColor   System Drawing Color Red             lblMessage Text    Please select  jpg image file to upload          Else             Dim FileSize As Integer   FileUpload1 PostedFile ContentLength              If FileSize  gt  1048576 Then                 lblMessage ForeColor   System Drawing Color Red                 lblMessage Text    File size  1MB  exceeded              Else                 Dim FileName As String   System IO Path GetFileName FileUpload1 FileName                   Dim ServerFileName As String   Server MapPath    Images Folder1     FileName                   If System IO File Exists ServerFileName    False Then                     FileUpload1 SaveAs Server MapPath    Images Folder1      FileUpload1 FileName                      lblMessage ForeColor   System Drawing Color Green                     lblMessage Text    File       FileUpload1 FileName     uploaded successfully                  Else                     lblMessage ForeColor   System Drawing Color Red                     lblMessage Text    File       FileName ToString       already exsist                  End If             End If         End If     Else         lblMessage ForeColor   System Drawing Color Red         lblMessage Text    Please select a file to upload      End If   FOR C  CODE                         if  FileUpload1 HasFile    true        string FileExtension   System IO Path GetExtension FileUpload1 FileName        if  FileExtension ToLower      jpg             lblMessage ForeColor   System Drawing Color Red          lblMessage Text    Please select  jpg image file to upload         else           int FileSize   FileUpload1 PostedFile ContentLength           if  FileSize  gt  1048576                lblMessage ForeColor   System Drawing Color Red              lblMessage Text    File size  1MB  exceeded             else               string FileName   System IO Path GetFileName FileUpload1 FileName                string ServerFileName   Server MapPath    Images Folder1     FileName                if  System IO File Exists ServerFileName     false                    FileUpload1 SaveAs Server MapPath    Images Folder1      FileUpload1 FileName                   lblMessage ForeColor   System Drawing Color Green                  lblMessage Text    File       FileUpload1 FileName     uploaded successfully                 else                   lblMessage ForeColor   System Drawing Color Red                  lblMessage Text    File       FileName ToString       already exsist                                   else       lblMessage ForeColor   System Drawing Color Red      lblMessage Text    Please select a file to upload

User · Answer

Can t comment yet  but I just wanted to disagree clarify with erikkallen     You should not just catch the exception in the situation you ve described   If you KNEW that the file should be there and due to some exceptional case  it wasn t  then it would be acceptable to just attempt to access the file and catch any exception that occurs     In this case  however  you are receiving input from a user and have little reason to believe that the file exists   Here you should always use File Exists     I know it is clich    but you should only use Exceptions for an exceptional event  not as part as the normal flow of your application   It is expensive and makes code more difficult to read follow

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