Can´t compare string from COM-object with string-literal

I have the following code in order to compare a value read from a DB with some expected values:

object o = row.get_Value(fieldIndex);
bool equal = o == "mytext";

When I debug that o has the value "mytext". However the comparison yields false. If on the other hand I cast o to string, the comparison works:

bool equal = (string)o == "mytext";

While row is a COM-object, o.GetType() returns string.

Unfortunately I cannot provide what get_Value does, as I don´t have its sourcecode.

So why does the second comparison work while the first one does not?

Solution

The minimal reproducible example would be

object o = "mymy";
string s = "my";
Console.WriteLine(o == s+s);

This gives you the compiler warning CS0252, which basically says that you get the equality comparison of object and not the equality comparison of string.

string changes the meaning of == to that of .Equals(), which tests for character by character equality.