How to convert c code fread to vb.net - c

Question

I`m writing the VB.net and need to call API(c language DLL)
My test sample code as follow
//Read Source File
char *SourceFilePath = "C:\\Docs\\Scandi\\attach\\verifyTest\\center.xml";
FILE *sourcefile= fopen(SourceFilePath, "rb");
if (!sourcefile)
{
printf("Error=%s\n", *SourceFilePath);
return;
}
fseek(sourcefile,0,SEEK_END);
long src_ch_len = ftell(sourcefile);
rewind(sourcefile);
unsigned char *src_ch =(unsigned char*)malloc(sizeof(char)*src_ch_len);
result = fread(src_ch,1,src_ch_len,sourcefile);
if(result!=src_ch_len)
{
printf("Reading Error=%s\n", *sourcefile);
return;
}
fclose(sourcefile);
//Read Data File
//Skip...
rc = BasicVerify(algorithm, data, dataLen, key, signature, signatureLen);
API Function definition
unsigned long verify(unsigned long algorithm, unsigned char *data, int dataLen,unsigned char *signature, int signatureLen, char *cerFile)
How to convert fopen(SourceFilePath, "rb") and fread(src_ch,1,src_ch_len,sourcefile) to VB.NET
Thanks

Answer 1

The analogue to fopen using the modes "rb" in VB .NET appears to be the FileStream class using the FileAccess.Read mode. From there you can use the FileStream.Read method as an analogue for fread. For example:
dim sourceFile as FileStream
sourceFile = new FileStream("C:\\Docs\\Scandi\\attach\\verifyTest\\center.xml", FileAccess.Read)
dim result as Integer
result = sourceFile.Read(array, 0, array.Length)
However, it seems from the fseek followed by ftell in your C code, you want to read the entire file into memory. This is often frowned upon since a file could be many gigabytes in size. If you really want to do that, use the File.ReadAllBytes method, for example:
dim src_ch as Byte()
src_ch = File.ReadAllBytes("C:\\Docs\\Scandi\\attach\\verifyTest\\center.xml")