I've got classes that look similar to the following: public class A<

Where queries break with nullable ints about sqlite-net HOT 1 CLOSED

praeclarum commented on September 13, 2024

Where queries break with nullable ints

from sqlite-net.

Comments (1)

fahimj commented on September 13, 2024

I think I had the similar problem with you. I tried to query with a nullable parameter, but it raised an exception saying, "Invalid cast from 'System.Int32' to 'System.Nullable`1[[System.Int32, mscorlib, Version=4.0.0.0,..."

Eventually I found some workaround. Here is my fix:

Open SQLite.cs file, and create ConvertTo method in class TableQuery

        private object ConvertTo(object obj, Type t)
        {
            Type u = Nullable.GetUnderlyingType(t);

            if (u != null)
            {
                if (obj == null)
                    return null;

                return Convert.ChangeType(obj, u);
            }
            else
            {
                return Convert.ChangeType(obj, t);
            }
        }

In method CompileExpr, search the following code:

                return new CompileResult {
                    CommandText = valr.CommandText,
                    Value = valr.Value != null ? Convert.ChangeType (valr.Value, ty, null) : null
                    };

and then replace it with:

                return new CompileResult {
                    CommandText = valr.CommandText,
                    Value = valr.Value != null ? ConvertTo(valr.Value, ty) : null
                    };


I got the ConvertTo method from http://stackoverflow.com/questions/793714/how-can-i-fix-this-up-to-do-generic-conversion-to-nullablet.  Changing Convert.ChangeType to ConvertTo method would fix up to do generic conversion to Nullable<T>. I don't know whether this is the best solution, but at least it works for me now.

from sqlite-net.

Where queries break with nullable ints about sqlite-net HOT 1 CLOSED

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