IQueryableExtension snippet for Effective c# blog.

IQueryableExtension.cs

public static IQueryable<T> StartsWith<T>(this IQueryable<T> source, Expression<Func<T, string>> stringProperty, 
                                          string searchTerm)
{
     if (string.IsNullOrEmpty(searchTerm))
     {
       return source;
     }

     var searchTermExpression = Expression.Constant(searchTerm);
     //Note Below instead of GetMethod("Contains") have used GetMethod(nameof(string.Contains))
     var startWithExpression = Expression.Call(stringProperty.Body, 
                                          typeof(string).GetMethod(nameof(string.StartsWith), 
                                                 new[] { typeof(string) }), searchTermExpression);
     var methodCallExpression = Expression.Call(typeof(Queryable), "Where", new Type[] { source.ElementType },
                                 source.Expression, 
                                     Expression.Lambda<Func<T, bool>>(startWithExpression, stringProperty.Parameters));
     return source.Provider.CreateQuery<T>(methodCallExpression);
}