Question

Fails:

object o = ((1==2) ? 1 : "test");

Succeeds:

object o;
if (1 == 2)
{
    o = 1;
}
else
{
    o = "test";
}

The error in the first statement is:

Type of conditional expression cannot be determined because there is no implicit conversion between ‘int’ and ‘string’.

Why does there need to be though, I’m assigning those values to a variable of type object.

Edit: The example above is trivial, yes, but there are examples where this would be quite helpful:

int? subscriptionID; // comes in as a parameter

EntityParameter p1 = new EntityParameter("SubscriptionID", DbType.Int32)
{
    Value = ((subscriptionID == null) ? DBNull.Value : subscriptionID),
}

Answer 1

use:

object o = ((1==2) ? (object)1 : "test");

The issue is that the return type of the conditional operator cannot be un-ambiguously determined. That is to say, between int and string, there is no best choice. The compiler will always use the type of the true expression, and implicitly cast the false expression if necessary.

Edit:
In you second example:

int? subscriptionID; // comes in as a parameter

EntityParameter p1 = new EntityParameter("SubscriptionID", DbType.Int32)
{
    Value = subscriptionID.HasValue ? (object)subscriptionID : DBNull.Value,
}

PS:
That is not called the ‘ternary operator.’ It is a ternary operator, but it is called the ‘conditional operator.’