Bug 4570 - Invalid cast exception on datareader.getbytes from sqlite's blob field
Summary: Invalid cast exception on datareader.getbytes from sqlite's blob field
Status: NEW
Alias: None
Product: Class Libraries
Classification: Mono
Component: Mono.Data.Sqlite ()
Version: 2.10.x
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: Untriaged
Assignee: Bugzilla
Depends on:
Reported: 2012-04-20 14:28 UTC by Natalia Portillo
Modified: 2015-01-28 13:24 UTC (History)
3 users (show)

Is this bug a regression?: ---
Last known good build:

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Description Natalia Portillo 2012-04-20 14:28:49 UTC
When trying to use SqliteDataReader.GetBytes() on a BLOB field inside a SQLite 3 database, an invalid cast exception is thrown.

Example code:
With schema "CREATE TABLE my_table (my_id INTEGER PRIMARY KEY, my_blob BLOB);"

string sql = "SELECT * FROM my_table";
SqliteCommand dbcmd = _dbcon.CreateCommand ();
dbcmd.CommandText = sql;
SqliteDataReader reader = dbcmd.ExecuteReader ();
while(reader.Read ())
    long blob_size = reader.GetBytes (reader.GetOrdinal("my_blob"), 0, null, 0, 0);

Exception Cannot cast from source type to destination type. happened.
Exception source: Mono.Data.Sqlite.
 Exception stack trace:   at Mono.Data.Sqlite.SqliteDataReader.VerifyType (Int32 i, DbType typ) [0x0011d] in /private/tmp/monobuild/build/BUILD/mono-2.10.9/mcs/class/Mono.Data.Sqlite/Mono.Data.Sqlite_2.0/SQLiteDataReader.cs:278 
  at Mono.Data.Sqlite.SqliteDataReader.GetBytes (Int32 i, Int64 fieldOffset, System.Byte[] buffer, Int32 bufferoffset, Int32 length) [0x00031] in /private/tmp/monobuild/build/BUILD/mono-2.10.9/mcs/class/Mono.Data.Sqlite/Mono.Data.Sqlite_2.0/SQLiteDataReader.cs:326 

Expected results would be blob_size to contain size of BLOB field in bytes.
Comment 1 Tyson 2014-07-08 16:45:00 UTC
What is the status of this bug?  It's still marked "NEW", but its over two years old.  And I just got the same error..

System.InvalidCastException: Cannot cast from source type to destination type.
  at at Mono.Data.Sqlite.SqliteDataReader.VerifyType (int,System.Data.DbType) <IL 0x00120, 0x009ac>
  at at Mono.Data.Sqlite.SqliteDataReader.GetBytes (int,long,byte[],int,int) <IL 0x00034, 0x001df>

private byte[] GetBytes(SqliteDataReader reader){
   const int CHUNK_SIZE = 2 * 1024;
   byte[] buffer = new byte[CHUNK_SIZE];
   long bytesRead;
   long fieldOffset = 0;
   using (MemoryStream stream = new MemoryStream()){
      //Error occurs on the next line..
      while ((bytesRead = reader.GetBytes(0, fieldOffset, buffer, 0, buffer.Length)) > 0){
          stream.Write(buffer, 0, (int)bytesRead);
          fieldOffset += bytesRead;
      return stream.ToArray();
Comment 2 Tyson 2015-01-28 13:24:08 UTC
I should add that I'm still getting this bug six months later, no one is assigned it, and I'm using Windows 7 (since i noticed this bug was marked for OSX)....