用于dbnull的数据转换。因为用convert.to无法转换dbnull类型

/// <summary>
/// add by wolf
/// </summary>
public static class ExtendObject
{
public static bool IsTargetType<T>(this object source) where T : IConvertible
{
Type targetType = typeof(T);

var tryParse = targetType.GetMethod("TryParse", BindingFlags.Static | BindingFlags.Public, Type.DefaultBinder,
new Type[] { typeof(T), targetType.MakeByRefType() },
new ParameterModifier[] { new ParameterModifier(2) });

if (tryParse == null)
return false;

var parameters = new object[] { source, Activator.CreateInstance(targetType) };

if (source is DBNull)
{
return false;
}
return (bool)tryParse.Invoke(null, parameters);
}

public static T ToTargetType<T>(this object source) where T : IConvertible
{
Type targetType = typeof(T);

var parse = targetType.GetMethod("Parse", BindingFlags.Static | BindingFlags.Public, Type.DefaultBinder,
new Type[] { typeof(object) },
new ParameterModifier[] { new ParameterModifier(1) });

if (parse == null)
return default(T);

return (T)parse.Invoke(null, new object[] { source });
}

public static T ToTargetTypeConvert<T>(this object source) where T : IConvertible
{
Type targetType = typeof(T);

return (T)Convert.ChangeType(source, targetType);

}

public static T AsTargetType<T>(this object source, T defaultValue) where T : IConvertible
{
if (source is DBNull)
{

}
object retunVal;
try
{
retunVal = source.ToTargetTypeConvert<T>();
}
catch (Exception)
{
return defaultValue;
}

return (T)retunVal;
}
}