'casting' with reflection

user_20047 0
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Consider the following sample code:

class SampleClass
{
    public long SomeProperty { get; set; }
}

public void SetValue(SampleClass instance, decimal value)
{
    // value is of type decimal, but is in reality a natural number => cast
    instance.SomeProperty = (long)value;
}

Now I need to do something similar through reflection:

void SetValue(PropertyInfo info, object instance, object value)
{
    // throws System.ArgumentException: Decimal can not be converted to Int64
    info.SetValue(instance, value)  
}

Note that I cannot assume that the PropertyInfo always represents a long, neither that value is always a decimal. However, I know that value can be casted to the correct type for that property.

How can I convert the 'value' parameter to the type represented by PropertyInfo instance through reflection ?

casting reflection c#
6 Answers

This is a very old question but I thought I'd chime in for ASP.NET Core Googlers.

In ASP.NET Core, .IsNullableType() is protected (amongst other changes) so the code is a tad different. Here's @jeroenh's answer modified to work in ASP.NET Core:

void SetValue(PropertyInfo info, object instance, object value)
{
    Type proptype = info.PropertyType;
    if (proptype.IsGenericType && proptype.GetGenericTypeDefinition().Equals(typeof(Nullable<>)))
    {
        proptype = new NullableConverter(info.PropertyType).UnderlyingType;
    }

    var convertedValue = Convert.ChangeType(value, proptype);
    info.SetValue(instance, convertedValue);
}
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