bavaza bavaza - 2 months ago 12
C# Question

C# Parse string to type known at runtime

I have a file holding some of the variables of a class, and each line is a pair : variable, value. I'm looking for a way to load these at runtime (a-la XmlSerializer), using reflection.

Is there a way to parse a string into a type known only at runtime?

The following is a wishful code sample where the last line (with the

pi.SetValue()
is not correct, because
PropertyType
is of class
Type
which does not have a generic
Parse()
method.

using (var sr = new StreamReader(settingsFileName))
{
String line;
while ((line = sr.ReadLine()) != null)
{
String[] configValueStrs = line.Trim().Split(seps);
PropertyInfo pi = configurableProperties.Single(p => p.Name == configValueStrs[0].Trim());
pi.SetValue(this, pi.PropertyType.Parse(configValueStrs[1].Trim()), null); <-- How do I manage this?
}
}


Since all of the relevant variables are Ints, Doubles, Strings or Booleans, as a last resort, I can Switch on the type and use the corresponding
ToType()
method, but I bet there is a more elegant solution.

Answer

You can use the static Convert.ChangeType method for that. It takes an object as its first parameter and a Type instance you want to convert the object to. The return value is of the type you requested or null if no suitable conversion was found. This method throw 4 different exceptions, from which three are caused by the value it tries to convert. You might want to catch and handle these.

Use the function as follows in your example:

// Convert.ChangeType can throw if the string doesn't convert to any known type
    pi.SetValue(this
      , Convert.ChangeType(configValueStrs[1], pi.PropertyType) 
      , null); 
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