Why Does Casting a SQL Float to a C# Float Throw an InvalidCastException?

Discrepancy between SQL Float and C# Float

When retrieving a value from a SQL database with a float datatype and attempting to assign it to a C# variable of type float, you may encounter an InvalidCastException. This is because the SQL float datatype corresponds to a double in C#.

Example:

Consider the following code:

DataRow exercise = _exerciseDataSet.Exercise.FindByExerciseID(65);
_AccelLimit = (float)exercise["DefaultAccelLimit"]; // Throws InvalidCastException

Reason for Exception:

The explicit cast from object to float in the above code cannot be performed because the underlying data type is a double. SQL floats are stored as 64-bit floating-point values, which are different from the 32-bit floating-point values represented by the C# float datatype.

Solution:

To resolve this issue, you can explicitly convert the retrieved value to a double before casting it to a float:

_AccelLimit = (float)(double)exercise["DefaultAccelLimit"];

This conversion ensures that the retrieved value is properly cast to a double, and then converted to a float to match the variable's declared data type.

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