internal static ArgumentException BodyShouldBeOfType(this LambdaExpression expression, string paramName,
params Type[] allowedTypes)
{
switch (allowedTypes.Length)
{
case 0:
throw new ArgumentException("At least one type needs to be allowed.", nameof(allowedTypes));
case 1:
return(expression.BodyShouldBeOfType(paramName, allowedTypes[0]));
default:
var sb = new StringBuilder();
foreach (var type in allowedTypes.Take(allowedTypes.Length - 2))
{
sb.Append(type.Name).Append(", ");
}
sb.Append(allowedTypes[allowedTypes.Length - 2]).Append(" or ")
.Append(allowedTypes[allowedTypes.Length - 1]);
return(expression.BodyShouldBeOfTypeImpl(paramName, sb.ToString()));
}
}
/// <summary> /// Return the body of the given lambda expression as the requested /// expression type. /// </summary> /// <typeparam name="T">The expected body expression type.</typeparam> /// <param name="expression">Lambda expression to extract the body from.</param> /// <returns>The body of the input expression.</returns> /// /// <exception cref="ArgumentException"> /// The body of <paramref name="expression"/> is not an instance of <typeparamref name="T"/>. /// </exception> public static T ExtractBody <T>(this LambdaExpression expression) where T : Expression => expression.Body as T ?? throw expression.BodyShouldBeOfType(nameof(expression), typeof(T));