multiple primitive types in a variable array raises System.ArgumentException: 'Object of type 'x' cannot be converted to type 'y'

[Paul-Fatovich]

Great library, however I am having an issue when mixing types in an array when using AddVariable.
For example:

const string outputFile = @"out.xlsx";

			var template = new XLTemplate(@"template.xlsx");
			var strings = new[] {
				"string",
				"1" ,
				"string",
				};

			var mixed = new[] {
				(object) "string",
				(object) 1 ,
				(object) "string",
				};

			
			template.AddVariable("strings", strings);
			template.AddVariable("mixed", mixed);
			template.Generate();

The mixed array will generate a System.ArgumentException: 'Object of type 'System.Int32' cannot be converted to type 'System.String' when the template is generated.

I looked through the source and the issue is in FormulaEvaluator.cs the constructor for the internal Parameter it is setting an expected type: i.e Expression.Parameter(value.GetType(), name)
however by changing it to ParameterExpression = Expression.Parameter(typeof(object), name);
the error no longer occurs.

The reason converting all values to strings is undesirable is, the generated excel file shows a warning: the number in the cell is formatted as text or preceded by a apostrophe.
This also causes a side effect that any number formatting on that cell will be ignored (like currency)

[Paul-Fatovich]

Did some further testing and looks like simply using typeof(object) does not work if it is a dynamic object because then lambda.DynamicInvoke(pars.Select(p => p.Value).ToArray()); fails in EvalNoCache with InvalidOperationException: Target object is not an ExpandoObject.

So would suggest checking if the value is simple type first and only then using typeof(object)

[b0bi79]

Fixed with #207