/// <summary>
/// Attempts to retrieve a parameter value from the given dictionary as described
/// by the parameter detail.
/// </summary>
/// <remarks>
/// If the parameter detail specifies a required parameter and the parameter is not
/// found in the dictionary, will throw a <c>KeyNotFoundException</c>. If the
/// parameter is found but not of the target type, an attempt is made to convert it.
/// Failing that, a <c>InvalidCastException</c> is thrown. If the parameter is found
/// and convertable to the target type, the action <c>a</c> will be invoked with its
/// resolved value.
/// </remarks>
public static IReadOnlyDictionary <string, object> GetParameter <T>(
this IReadOnlyDictionary <string, object> initParams, ParameterDetail p, Action <T> a)
{
if (TryGetValue <T>(initParams, p, out var value))
{
a(value);
}
else if (p.IsRequired)
{
throw new KeyNotFoundException($"missing required parameter [{p.Name}]");
}
return(initParams);
}
/// <summary>
/// Tries to retrieve a value from the parameters dictionary of the specified target type.
/// </summary>
/// <returns>
/// true if able to retrieve a parameter value of the target name and type
/// </returns>
/// <remarks>
/// If a value is found for the given name, but does not match the target type,
/// then every attempt is made to convert the value to the target type. Failing
/// that, an <c>InvalidCastException</c> is thrown.
/// </remarks>
public static bool TryGetValue <T>(this IReadOnlyDictionary <string, object> initParams,
ParameterDetail p, out T value)
{
if (initParams.TryGetValue(p.Name, out var val))
{
if (val is null)
{
value = default(T);
}
else if (!(val is T))
{
var valType = val.GetType();
var targType = typeof(T);
// Make our best effort to convert to or from
var valTypeConverter = TypeDescriptor.GetConverter(valType);
if (valTypeConverter.CanConvertTo(targType))
{
val = (T)valTypeConverter.ConvertTo(val, targType);
}
else
{
var targTypeConverter = TypeDescriptor.GetConverter(targType);
if (targTypeConverter.CanConvertFrom(valType))
{
val = (T)targTypeConverter.ConvertFrom(val);
}
else
{
throw new InvalidCastException($"cannot convert type" +
$" [{valType.FullName}] to parameter [{p.Name}] type of" +
$" [{targType.FullName}]");
}
}
}
value = (T)val;
return(true);
}
value = default(T);
return(false);
}