Question

Possible Duplicate:
Nullable types and the ternary operator. Why won’t this work?

for example:

int? taxid;
if (ddlProductTax.SelectedValue == "") {
  taxid = null; } 
else {
  taxid = Convert.ToInt32(ddlProductTax.SelectedValue);
} //Correct

But

int? taxid;
taxid = (ddlProductTax.SelectedValue == "" ? null : Convert.ToInt32(ddlProductTax.SelectedValue)); //Error

It error say and int32 cannot implicit convert.

The ( ? truepart : falsepart); is not short of (if ..else..) ?

Answer 1

The last two operands of the ternary operator should both yield the same type.

Cast either side to int?:

taxid = ddlProductTax.SelectedValue == "" ?
                                 (int?)null
                                 : Convert.ToInt32(ddlProductTax.SelectedValue); 

You can see the exact behavior in the specification:

• 7.12 Conditional operator
• 6.1 Implicit conversions