SQLite exception using String.Format args - wrong syntax?

this is my very first question, so excuse me if I am missing something or doing something wrong :)

Project
I am writing a .NET Application (Visual C# 2012 Express) which uses the ADO.NET System.Data.SQLite and has the task to search for SQLite databases in a specified folder. After that you can choose one or multiple DBs from a listview which will then get exported to HTML/CSV. Export in this case means:
- all data from database is getting read (tables/columns)
- null/empty databases are getting dropped before final export
- null/empty tables are getting dropped before final export
- null/empty columns are getting dropped before final export

Problem
To drop empty columns I am using the following SQLite statement for the CommandText:

object validation = null;
query.CommandText = String.Format("SELECT COUNT({0}) FROM {1} WHERE {0} IS NOT NULL AND {0} <> '';", header, table);
validation = query.ExecuteScalar();

Unfortunately this is causing ExecuteScalar() to throw an exception on one database, but works fine for all others.

If I am 'single quoting' arguments like so...

object validation = null;
query.CommandText = String.Format("SELECT COUNT('{0}') FROM '{1}' WHERE '{0}' IS NOT NULL AND '{0}' <> '';", header, table);
validation = query.ExecuteScalar();

... there will be no exception, but then null/empty columns in other databases are not getting dropped because the ExecuteScalar() result is not correct.

EDIT: Table: raw_contacts | Header: sort_key
bei System.Data.SQLite.SQLite3.Prepare(SQLiteConnection cnn, String strSql, SQLiteStatement previous, UInt32 timeoutMS, String& strRemain)
bei System.Data.SQLite.SQLiteCommand.BuildNextCommand()
bei System.Data.SQLite.SQLiteCommand.GetStatement(Int32 index)
bei System.Data.SQLite.SQLiteDataReader.NextResult()
bei System.Data.SQLite.SQLiteDataReader..ctor(SQLiteCommand cmd, CommandBehavior behave)
bei System.Data.SQLite.SQLiteCommand.ExecuteReader(CommandBehavior behavior)
bei System.Data.SQLite.SQLiteCommand.ExecuteScalar(CommandBehavior behavior)
bei System.Data.SQLite.SQLiteCommand.ExecuteScalar()  

EDIT: header and table are strings which are gathered from a foreach-loop out of a string[].

So this seems just like a syntax fault to me. If you need more information or code, just tell me.
But what to do now? Who can help me?

Thank You!
Ben-X