LINQ to Entities無法識別方法'System.String格式

Question

我該如何重構此LINQ以使其工作？

var a = (from app in mamDB.Apps where app.IsDeleted == false 
       select string.Format("{0}{1}",app.AppName, 
       app.AppsData.IsExperimental? " (exp)": string.Empty)) 
       .ToArray();} 

我現在得到的錯誤：

LINQ to Entities does not recognize the method 'System.String Format(System.String, System.Object, System.Object)' method, and this method cannot be translated into a store expression.

我已經白白嘗試：

return (from app in mamDB.Apps where app.IsDeleted == false 
     select new string(app.AppName + (app.AppsData != null && 
     app.AppsData.IsExperimental)? " (exp)": string.Empty)).ToArray(); 

Answer 1

你可以做string.Format回到LINQ到對象：

var a = (from app in mamDB.Apps where app.IsDeleted == false 
     select new {app.AppName, app.AppsData.IsExperimental}) 
     .AsEnumerable() 
     .Select(row => string.Format("{0}{1}", 
      row.AppName, row.IsExperimental ? " (exp)" : "")).ToArray(); 

Answer 2

試試這個

var a = (from app in mamDB.Apps where app.IsDeleted == false 
      select new {AppName = app.AppName, IsExperimental = app.AppsData.IsExperimental}) 
      .Select(app => string.Format("{0}{1}",app.AppName, 
      app.IsExperimental? " (exp)": string.Empty)) 
      .ToArray();}