However, when I try to deserialize a TFileStream, Delphi raises the exception EVariantTypeCastError: \’Could not convert variant of type (Empty) into type ($0996)\’. The file stream contains a TClientDataSet (that has been saved to a file).

How can I solve the problem?

However, my goal was to show how to (de)serialize variants, and such details like position in the stream can be handled by developers themselves. That’s why I won’t edit the code in the post.

These two functions are mine as well, but I forgot to provide the code for them. They don’t do anything much special, I use them as kind of C macros.

Here they are.

function IsSimpleType (VarType: word) : boolean;
begin
Result := (VarType and varTypeMask) in
[varByte, varSmallint, varInteger, varSingle, varDouble, varCurrency, varDate, varError, varBoolean];
end;

function GetSimpleTypeSize (VarType: word): integer;
begin
case VarType and varTypeMask of
varSmallint: Result := SizeOf (Smallint);
varInteger: Result := SizeOf (Integer);
varSingle: Result := SizeOf (Single);
varDouble: Result := SizeOf (Double);
varCurrency: Result := SizeOf (Currency);
varDate: Result := SizeOf (Double);
varError: Result := SizeOf (Longint);
varBoolean: Result := SizeOf (Boolean);
varByte: Result := SizeOf (Byte);
else
Result := -1;
end;
end;

Keep up the good work!