/// <summary>
/// Test if the input value is a non-null numeric type
/// or a string that can be parsed as a number, with detection
/// of hex strings controlled by ConvertOptions flags
/// </summary>
/// <param name="value"></param>
/// <param name="options"></param>
public static bool IsNumeric(object value, ConvertOptions options)
{
if (value == null)
{
return(false);
}
if (value is string sValue)
{
if (double.TryParse(sValue, out double d))
{
return(true);
}
if (options.HasFlag(ConvertOptions.AllowVBHex) && Regex.IsMatch(sValue, @"^\s*&[hH][0-9a-fA-F]+$"))
{
return(true);
}
if (options.HasFlag(ConvertOptions.Allow0xHex) && Regex.IsMatch(sValue, @"^\s*0[xX][0-9a-fA-F]+$"))
{
return(true);
}
return(false);
}
return(TypeInspection.IsNumberType(value.GetType()));
}
internal static object To(object value, Type targetType, ConvertOptions options, bool ignoreError, object defaultValue)
{
var typeInfo = targetType.GetTypeInfo();
// Quick check #1: If input is null reference and target type is a reference type we can always safely return nothing
if ((value == null) && (!typeInfo.IsValueType))
{
return(null);
}
// Quick check #2: If the input already is of the target type the return it immediately
if (targetType.IsInstanceOfType(value))
{
return(value);
}
if (typeInfo.IsValueType)
{
// ---------------------------------------------------------------------------
// Special treatment of Nullable<T>. Although both C# and VB allow assignment
// and comparison of null literal to Nullable<T> values, the underlying type
// is actually a non-nullable struct (value type), thus we handle nullable
// types inside the section that handles value types
// ---------------------------------------------------------------------------
if (TypeInspection.IsNullableOfT(targetType))
{
if (ValueInspection.IsNull(value, options))
{
// Nullable<T> of T is technically a struct, so IsValueType is true. However,
// semantics and implementation allow it to be treated as a reference type,
// so return null if the input is empty
return(null);
}
else
{
// Input is not an empty value, so convert to the underying type
try
{
// Note: DON'T ignore error on underlying conversion type
return(To(value, Nullable.GetUnderlyingType(targetType), options, false, null));
}
catch
{
if (ignoreError)
{
return(defaultValue ?? null);
}
throw;
}
}
} // end IsNullable<T>
// If input is empty, we can immediately return default or throw an exception
if (ValueInspection.IsNull(value, options))
{
if (options.HasFlag(ConvertOptions.NullToValueDefault))
{
//This is how we return the default value of a value type:
return(defaultValue ?? Activator.CreateInstance(targetType));
}
else
{
if (ignoreError)
{
return(defaultValue ?? Activator.CreateInstance(targetType));
}
throw new ArgumentNullException("value", "Cannot convert empty input value to value type " + targetType.FullName);
}
}
// We only got this far if the target type is a value type and the input value is not empty
try
{
// ---------------------------------------------------------------------------
// Special treatment of Enums
// ---------------------------------------------------------------------------
if (typeInfo.IsEnum)
{
// Test IsNumeric BEFORE testing string so that numeric strings are
// treated as numbers, not as enum member names
if (ValueInspection.IsNumeric(value, options))
{
// If the input is a number or *numeric string*, first convert the
// input to an enum number value, then cast it using Enum.ToObject
// Note: DON'T ignore error on underlying conversion type
var rawValue = To(value, Enum.GetUnderlyingType(targetType), options, false, null);
return(Enum.ToObject(targetType, rawValue));
}
else if (value is string)
{
// Input is a string but Information.IsNumeric did not recognize it
// as a number. So, treat the input as an enum member name
string sEnumName = Regex.Replace((string)value, @"[\s\r\n]+", "");
return(Enum.Parse(targetType, sEnumName, true));
}
else
{
// Fallback: Attempt to convert the input to the underlying numeric type, even if
// Information.IsNumeric returned false
// Note: DON'T ignore error on underlying conversion type
var rawValue = To(value, Enum.GetUnderlyingType(targetType), options, false, null);
return(Enum.ToObject(targetType, rawValue));
}
} // end IsEnum
// ---------------------------------------------------------------------------
// Use hand-written conversion functions for specific types
// ---------------------------------------------------------------------------
if (targetType == typeof(Guid))
{
// Use special conversion logic for converting to a Guid
return(_ToGuid(value));
}
else if (targetType == typeof(TimeSpan))
{
// Use special conversion logic for converting to a TimeSpan
return(_ToTimeSpan(value));
}
else if (targetType == typeof(bool))
{
// Use special conversion logic for converting to Boolean
return(_ToBool(value));
}
// ---------------------------------------------------------------------------
// Invoke IConvertible implementation, if any
// ---------------------------------------------------------------------------
if (value is IConvertible iConvertible)
{
// Use the System.ChangeType method, which makes full use of any IConvertible implementation on the target type
try
{
return(System.Convert.ChangeType(value, targetType));
}
catch
{
// Ignore exception and fall back to VBConvert implementation
}
}
// ---------------------------------------------------------------------------
// Fall back to VBConvert methods
// ---------------------------------------------------------------------------
switch (System.Convert.GetTypeCode(targetType))
{
case TypeCode.Boolean:
// Use custom ToBool method
return(_ToBool(value));
case TypeCode.Byte:
return(VBConvert.ToByte(value));
case TypeCode.Char:
return(VBConvert.ToChar(value));
case TypeCode.DateTime:
return(VBConvert.ToDate(value));
case TypeCode.Decimal:
return(VBConvert.ToDecimal(value));
case TypeCode.Double:
return(VBConvert.ToDouble(value));
case TypeCode.Int16:
return(VBConvert.ToShort(value));
case TypeCode.Int32:
return(VBConvert.ToInteger(value));
case TypeCode.Int64:
return(VBConvert.ToLong(value));
case TypeCode.SByte:
return(VBConvert.ToSByte(value));
case TypeCode.Single:
return(VBConvert.ToSingle(value));
case TypeCode.String:
return(VBConvert.ToString(value));
case TypeCode.UInt16:
return(VBConvert.ToUShort(value));
case TypeCode.UInt32:
return(VBConvert.ToUInteger(value));
case TypeCode.UInt64:
return(VBConvert.ToULong(value));
}
// ---------------------------------------------------------------------------
// Fall back to VBConvert.ChangeType
// ---------------------------------------------------------------------------
return(VBConvert.ChangeType(value, targetType));
}
catch (Exception ex)
{
// Conversion of non-empty value to value type failed.
if (ignoreError)
{
return(defaultValue ?? Activator.CreateInstance(targetType));
}
throw new InvalidCastException($"Cannot convert {_FormatValue(value)} to type {targetType.FullName}", ex);
}
} // end IsValueType
else
{
// Reference types...not much to do here besides check for empty values
if (ValueInspection.IsNull(value, options))
{
return(null);
}
try
{
// Fall back to VBConvert.ChangeType
return(VBConvert.ChangeType(value, targetType));
}
catch
{
if (ignoreError)
{
return(defaultValue ?? null);
}
throw;
}
}
}
/// <summary>
/// Test whether the input value is null or DBNull. Will also return true if <paramref name="options"/>
/// includes the <see cref="ConvertOptions.EmptyStringAsNull"/> flag and <paramref name="value"/> is an empty string.
/// </summary>
public static bool IsNull(object value, ConvertOptions options)
{
return(IsNull(value, options.HasFlag(ConvertOptions.EmptyStringAsNull)));
}