Let’s say we want to convert int to short with a bounds check. Is there a difference between checked((short)x) and Convert.ToInt16(x)?

Behavior

The behavior is the same for both methods: if the value is out of bounds, an OverflowException is thrown.

Performance

Benchmark results:

|      Method |        Val |          Mean |      Error |     StdDev | Ratio | RatioSD |
|------------ |----------- |--------------:|-----------:|-----------:|------:|--------:|
| CheckedCast |          1 |     0.3265 ns |  0.0030 ns |  0.0028 ns |  1.00 |    0.00 |
|   ConvertTo |          1 |     1.1499 ns |  0.0044 ns |  0.0042 ns |  3.52 |    0.03 |
|             |            |               |            |            |       |         |
| CheckedCast | 2147483647 | 6,430.8317 ns | 10.7705 ns | 10.0747 ns |  1.00 |    0.00 |
|   ConvertTo | 2147483647 | 6,405.4382 ns | 20.2827 ns | 18.9725 ns |  1.00 |    0.00 |

Checked cast is 3.5 times faster when there is no exception.

Generated Code

Checked cast is compiled into a single conv.ovf.i2 instruction.

Convert.ToInt16 method uses an explicit bounds check and then an unchecked cast (conv.i2):

public static short ToInt16(int value)
{
    if (value < short.MinValue || value > short.MaxValue) ThrowInt16OverflowException();
    return (short)value;
}

Conclusion

With Convert.ToInt16(x) it is not immediately clear if the bounds check is performed or not.

Checked cast is faster, generates less code, and carries the intent better.