why can't you assign a number with a decimal point to decimal type directly without using type suffix?

Question

Why can't you assign a number with a decimal point to the decimal type directly without using type suffix? isn't this kind of number considered a number of type decimal?

decimal bankBalance = 3433.20; // ERROR! 

Answer 1

Edit: I may have missed the last part of the question, so the overview below is hardly useful.

Anyway, the reason you can't do what you're trying to do is because there is no implicit conversion between floating point types and decimal. You can however assign it from an integer, as there is an implicit conversion from int to decimal.

---

You can, but you have to use this syntax (or do an explicit cast to decimal).

decimal bankBalance = 3433.20m; 

and for floats it is

float bankBalance = 3433.20f; 

default is double

double bankBalance = 3444.20; 

Answer 2

Actually, hidden spec feature: you can ;-p

decimal bankBalance = (decimal)3433.20; 

This is genuinely parsed by the compiler as a decimal (not a float and a cast). See the IL to prove it. Note that the precision gets truncated, though (this has 1 decimal digit, not the 2 you get from the M version).

IL generated:

L_0001: ldc.i4 0x861c L_0006: ldc.i4.0  L_0007: ldc.i4.0  L_0008: ldc.i4.0  L_0009: ldc.i4.1  L_000a: newobj instance void [mscorlib]System.Decimal::.ctor(int32, int32, int32, bool, uint8) L_000f: stloc.0  

Compared to:

decimal bankBalance = 3433.20M; 

Which generates:

L_0001: ldc.i4 0x53d18 L_0006: ldc.i4.0  L_0007: ldc.i4.0  L_0008: ldc.i4.0  L_0009: ldc.i4.2  L_000a: newobj instance void [mscorlib]System.Decimal::.ctor(int32, int32, int32, bool, uint8) L_000f: stloc.0  

The only difference is the decimal digits (1 vs 2, and a factor of 10, accordingly)