// --------------------------------------------------------------------------------------------------------------------
public static object ChangeType(object value, Type targetType, IFormatProvider provider = null)
{
if (targetType == null)
{
throw new ArgumentNullException("targetType");
}
if (value == DBNull.Value)
{
value = null;
}
var valueType = value != null?value.GetType() : typeof(object);
if (valueType == targetType || targetType.IsAssignableFrom(valueType))
{
return(value); // (same type as target! [or at least compatible])
}
if (provider == null)
{
provider = Thread.CurrentThread.CurrentCulture;
}
var targetUnderlyingType = Nullable.GetUnderlyingType(targetType);
if (targetUnderlyingType != null)
{
if (value == null)
{
return(value);
}
// ... this is a nullable type target, so need to convert to underlying type first, then to a nullable type ...
value = ChangeType(value, targetUnderlyingType, provider); // (recursive call to convert to the underlying nullable type)
return(Activator.CreateInstance(targetType, value));
}
else if (targetType == typeof(string))
{
return(value != null?value.ToString() : "");
}
else if (targetType == typeof(Boolean))
{
if (value == null || value is string && ((string)value).IsNullOrWhiteSpace()) // (null or empty strings will be treated as 'false', but explicit text will try to be converted)
{
value = false;
}
else if (Utilities.IsNumeric(valueType))
{
value = Convert.ToDouble(value) != 0; // (assume any value other than 0 is true)
}
else if ((value = Utilities.ToBoolean(value, null)) == null)
{
throw new InvalidCastException(string.Format("Types.ChangeType(): Cannot convert string value \"{0}\" to a Boolean.", value));
}
return(value); // (this has the correct type already, so just return now)
}
else if (targetType.IsValueType && targetType.IsPrimitive)
{
if (value == null || value is string && ((string)value).IsNullOrWhiteSpace())
{
// ... cannot set values to 'null' or empty strings, so translate this to a value type before conversion ...
if (targetType == typeof(bool))
{
value = false;
}
else if (targetType == typeof(DateTime))
{
value = DateTime.MinValue;
}
else
{
value = 0;
}
}
else if (value is string)
{
// ... a value type is expected, but 'value' is a string, so try converting the string to a number value first in preparation ...
double d;
if (double.TryParse((string)value, System.Globalization.NumberStyles.Any, provider, out d))
{
value = d;
}
}
}
else if (value == null)
{
return(null);
}
try
{
return(Convert.ChangeType(value, targetType, provider));
}
catch (Exception ex)
{
throw new InvalidCastException(string.Format("Types.ChangeType(): Cannot convert value \"{0}\" (type: '{1}') to type '{2}'. If you are developing the source type yourself, implement the 'IConvertible' interface.", Utilities.ND(value, ""), value.GetType().FullName, targetType.FullName), ex);
}
}
