Edit Question - KnowledgeHub

Title Body

Summary of the problem: For some decimal values, when we convert the type from decimal to double, a small fraction is added to the result. What makes it worse, is that there can be two "equal" decimal values that result in different double values when converted. Code sample: decimal dcm = 8224055000.0000000000m; // dcm = 8224055000 double dbl = Convert.ToDouble(dcm); // dbl = 8224055000.000001 decimal dcm2 = Convert.ToDecimal(dbl); // dcm2 = 8224055000 double dbl2 = Convert.ToDouble(dcm2); // dbl2 = 8224055000.0 decimal deltaDcm = dcm2 - dcm; // deltaDcm = 0 double deltaDbl = dbl2 - dbl; // deltaDbl = -0.00000095367431640625 Look at the results in the comments. Results are copied from debugger's watch. The numbers that produce this effect have far less decimal digits than the limit of the data types, so it can't be an overflow (I guess!). What makes it much more interesting is that there can be two equal decimal values (in the code sample above, see "dcm" and "dcm2", with "deltaDcm" equal to zero) resulting in different double values when converted. (In the code, "dbl" and "dbl2", which have a non-zero "deltaDbl") I guess it should be something related to difference in the bitwise representation of the numbers in the two data types, but can't figure out what! And I need to know what to do to make the conversion the way I need it to be. (like dcm2 -> dbl2)

Tags (comma-separated) Cancel