error in the function ParameterValueForSQL, if the value is null,

there should be a test on the value.

Do you feel the
retval = "'" + sp.Value.ToString().Replace("'", "''") + "'";
is correct for DateTime?

I'm getting localized Dates in Greek when I use it via CommandAsSql library.

In the library code it also uses later on sb.Append("'").Append(Convert.ToDateTime(dr[colIndex]).ToString("yyyy-MM-dd HH:mm")).Append("'");
for handling structure types which seems more logical to use everywhere

I mean the .ToString("yyyy-MM-dd HH:mm") - not sure about the DateTimeOffset and DateTime2, guess for those too

The .travis.yml file is broken. It needs to build, (run tests) and if succeeded, pack and push to nuget.
It has several issues.
one of them: Cannot open assembly 'nuget.exe': No such file or directory.
And I have tried several things as you can see in the commits. So I could use some help here.

Shouldn't GUID values be enclosed in quotes?