/// <summary>
/// Creates or throws a converter.
/// </summary>
internal static IValueConverter <TValue> CreateOrThrow <TValue>()
{
var created =
StringConverter <TValue> .TryCreate(out var converter) ||
ParseConverter <TValue> .TryCreate(out converter) ||
EnumConverter <TValue> .TryCreate(out converter) ||
NullableTypeParseConverter <TValue> .TryCreate(out converter) ||
NullableEnumConverter <TValue> .TryCreate(out converter) ||
ConstructorConverter <TValue> .TryCreate(out converter) ||
CastConverter <TValue> .TryCreate(out converter);
if (created)
{
return(converter !);
}
throw ConfigurationExceptions.NoDefaultConverter <TValue>();
}
/// <summary>
/// Tries to create an instance.
/// </summary>
internal static bool TryCreate(out IValueConverter <TValue>?converter)
{
converter = null;
var nullableType = typeof(TValue);
if (!nullableType.IsNullableType())
{
return(false);
}
var underlyingType = nullableType.GetGenericArguments()[0];
if (!underlyingType.IsEnum)
{
return(false);
}
var strParamExpr = Expression.Parameter(typeof(string), "str");
var constTypeExpr = Expression.Constant(underlyingType);
var trueExpr = Expression.Constant(true);
var callParseExpr = Expression.Call(TypeHelpers.GetEnumParseMethodInfo(), constTypeExpr, strParamExpr, trueExpr);
var convertExpr = Expression.Convert(callParseExpr, nullableType);
var defaultExpr = Expression.Default(nullableType);
var callIsNullOrWsExpr = Expression.Call(TypeHelpers.StringIsNullOrWhiteSpaceMethodInfo, strParamExpr);
var conditionExpr = Expression.Condition(callIsNullOrWsExpr, defaultExpr, convertExpr);
var lambdaExpr = Expression.Lambda <Func <string, TValue> >(conditionExpr, strParamExpr);
var function = lambdaExpr.Compile();
converter = new NullableEnumConverter <TValue>(value =>
{
try
{
return(function(value));
}
catch (ArgumentException)
{
throw Exceptions.EnumConversionFailed(underlyingType, value);
}
});
return(true);
}
