Microsoft.VisualStudio.Project.ProjectElement.GetMetadataAndThrow C# (CSharp) Method

        public string GetMetadataAndThrow(string attributeName, Exception exception)
        {
            if (attributeName == null)
                throw new ArgumentNullException("attributeName");
            if (string.IsNullOrEmpty(attributeName))
                throw new ArgumentException("attributeName cannot be null or empty");
            if (HasItemBeenDeleted)
                throw new InvalidOperationException("The item has been deleted.");

            Debug.Assert(!String.IsNullOrEmpty(attributeName), "Cannot retrieve an attribute for a null or empty attribute name");
            string attribute = GetMetadata(attributeName);

            if(String.IsNullOrEmpty(attributeName) && exception != null)
            {
                if(String.IsNullOrEmpty(exception.Message))
                {
                    Debug.Assert(!String.IsNullOrEmpty(this.ProjectManager.BaseUri.AbsoluteUrl), "Cannot retrieve an attribute for a project that does not have a name");
                    string message = String.Format(CultureInfo.CurrentCulture, SR.GetString(SR.AttributeLoad, CultureInfo.CurrentUICulture), attributeName, this.ProjectManager.BaseUri.AbsoluteUrl);
                    throw new InvalidOperationException(message, exception);
                }

                throw exception;
            }

            return attribute;
        }

        /// <summary>
        /// Get information from the registry based for the project
        /// factory corresponding to the TypeGuid of the element
        /// </summary>
        private RegisteredProjectType GetRegisteredProject(ProjectElement element)
        {
            ProjectElement elementToUse = (element == null) ? this.nestedProjectElement : element;

            if (elementToUse == null)
            {
                throw new ArgumentNullException("element");
            }

            // Get the project type guid from project elementToUse
            string typeGuidString     = elementToUse.GetMetadataAndThrow(ProjectFileConstants.TypeGuid, new Exception());
            Guid   projectFactoryGuid = new Guid(typeGuidString);

            EnvDTE.DTE dte = this.ProjectMgr.Site.GetService(typeof(EnvDTE.DTE)) as EnvDTE.DTE;
            Debug.Assert(dte != null, "Could not get the automation object from the services exposed by this project");

            if (dte == null)
            {
                throw new InvalidOperationException();
            }

            RegisteredProjectType registeredProjectType = RegisteredProjectType.CreateRegisteredProjectType(projectFactoryGuid);

            Debug.Assert(registeredProjectType != null, "Could not read the registry setting associated to this project.");
            if (registeredProjectType == null)
            {
                throw new InvalidOperationException();
            }
            return(registeredProjectType);
        }