C# Unable to cast object of type 'System.Double' to type 'System.Single'
Solution 1
When you add to the dictionary your double will be boxed, as the dictionary is mapping a string
to an object
.
When you unbox you must cast to the underlying type. In your case that underlying type is a double
, so the cast to float
will fail.
You can get around this by using Convert.ToSingle
netPlannedHours = Convert.ToSingle(d["key"])
This method will work out the underlying type and can do the conversion, at the expense of a performance hit when working out the type conversions.
Solution 2
I had a similar problem today with my SQL entity mapped as "float" and my .Net entity mapped as "float". I kept the SQL mapping, though changed the .Net types to "double".
The ADO.NET SQL Server Data Type Mappings documentation presents a table of the correct mapping for all types.
With A SpiRIT
Updated on October 28, 2021Comments
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With A SpiRIT about 2 years
before judging that this question is already answered, please read the description. I have this simple code below:
Dictionary<string, object> d = new Dictionary<string, object>(); d.Add("key" , 30d); System.Diagnostics.Debug.WriteLine($" TYPE OF OBJECT IS \"{d["key"].GetType()}\""); netPlannedHours = (float)d["key"]; ---> **Line of Interest**
When i execute this i get:
TYPE OF OBJECT IS "System.Double" Exception thrown: 'System.InvalidCastException' in DevOpsAutomatedReporting.dll Unable to cast object of type 'System.Double' to type 'System.Single'.
The exception is caused by the last line tagged "Line of interest". I can't really understand why the last line is causing this as the type of the object is inferred to be "System.Double" at runtime so it should've had cast it to a float but it doesn't. An interesting point is that if i replace the last line ("Line of interest") with either of the following two lines of code it successfully converts the double to float
// Cast the double object to double again and then to float **WORKS** netPlannedHours = (float)(double)d["key"]; // Convert to float using "Convert.ToSingle()" **WORKS** netPlannedHours = Convert.ToSingle(d["key"]);
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Serg over 4 years.. as the dictionary is mapping a
double
... I guess -
Martin Kinuthia almost 2 yearsThis is a very good solution when you're mapping SQL entity with .Net entity so if you're experiencing the same problem check it out