问题
I want to to convert an Object to a type that will be assigned at runtime.
For example, assume that I have a function that assigns a string value(from a TextBox or Dropdownlist
) to an Object.Property
.
How would I convert the value to proper type? For instance, it could be an integer, string, or enum.
Public void Foo(object obj,string propertyName,object value)
{
//Getting type of the property og object.
Type t= obj.GetType().GetProperty(propName).PropertyType;
//Now Setting the property to the value .
//But it raise an error,because sometimes type is int and value is "2"
//or type is enum (e.a: Gender.Male) and value is "Male"
//Suppose that always the cast is valid("2" can be converted to int 2)
obj.GetType().GetProperty(propName).SetValue(obj, value, null);
}
回答1:
You need to use the Convert.ChangeType(...) function (the input could just as easily be an object ... I just had a string version pre-baked):
/// <summary>
/// Sets a value in an object, used to hide all the logic that goes into
/// handling this sort of thing, so that is works elegantly in a single line.
/// </summary>
/// <param name="target"></param>
/// <param name="propertyName"></param>
/// <param name="propertyValue"></param>
public static void SetPropertyValueFromString(this object target,
string propertyName, string propertyValue)
{
PropertyInfo oProp = target.GetType().GetProperty(propertyName);
Type tProp = oProp.PropertyType;
//Nullable properties have to be treated differently, since we
// use their underlying property to set the value in the object
if (tProp.IsGenericType
&& tProp.GetGenericTypeDefinition().Equals(typeof(Nullable<>)))
{
//if it's null, just set the value from the reserved word null, and return
if (propertyValue == null)
{
oProp.SetValue(target, null, null);
return;
}
//Get the underlying type property instead of the nullable generic
tProp = new NullableConverter(oProp.PropertyType).UnderlyingType;
}
//use the converter to get the correct value
oProp.SetValue(target, Convert.ChangeType(propertyValue, tProp), null);
}
回答2:
A universal Type Converter is what you seek !? Not an easy feat..
Try this approach:
Universal Type Converter
You can in NuGet Install-Package UniversalTypeConverter
Also, is using Generics
out of the question here? It would facilitate the solution if you know at least the target type of the conversion.
回答3:
Here's another way you can do it, but I'm not sure
Without support for generic types:
public void Foo(object obj,string propertyName,object value)
{
//Getting type of the property og object.
Type type = obj.GetType().GetProperty(propertyName).PropertyType;
obj.GetType().GetProperty(propertyName).SetValue(obj, Activator.CreateInstance(type, value), null);
}
With support for generic types:
public void Foo(object obj,string propertyName,object value)
{
//Getting type of the property og object.
Type type = obj.GetType().GetProperty(propertyName).PropertyType;
if (type.IsGenericType)
type = type.GetGenericArguments()[0];
obj.GetType().GetProperty(propertyName).SetValue(obj, Activator.CreateInstance(type, value), null);
}
回答4:
I'm not sure it works, but give it a try:
public static T To<T>(this IConvertible obj)
{
return (T)Convert.ChangeType(obj, typeof(T));
}
Public void Foo(object obj,string propertyName,object value)
{
Type t= obj.GetType().GetProperty(propName).PropertyType;
obj.GetType().GetProperty(propName).SetValue(obj, value.To<t>(), null);
}
回答5:
I used the Convert function in C#. The way I'm doing my conversion is using reflection.:
Type type = this.myObject.GetType();
if (type.Name == "MyObjectClass") {
var Voucherrequest = (MyObjectClass)Convert.ChangeType(myObject, typeof(MyObjectClass));
This is all assuming you know what type you want to convert into. You can even make a switch and have multiple types you want to reflect too.
来源:https://stackoverflow.com/questions/7616177/convert-to-a-type-on-the-fly-in-c-net