July 5, 2016

Using LINQ for Queries

LINQ?is?very?good?and?efficient?when?it?comes?to?handling?data?coming?from?a?datasource.?This?little?example?creates?a?Table?object.?Then?creates?a?DataContext?to?interpret?the?Table?data,?and?finally?does?a?query?to?extract?the?wanted?data. ????????[Table(Name?=?”Courses”)] ????????public?class?Courses?//Create?Courses?Table ????????{ ????????????[Column(IsPrimaryKey?=?true,?DbType?=?”BIGINT?NOT?NULL?IDENTITY”,?IsDbGenerated?=?true)] ????????????public?Int32?CourseID;?//Field ????????????[Column] ????????????public?string?CourseDesc;?//Field ????????} ????????????????using?(DataContext?dcCourses?=?new?DataContext(“CONNECTION_STRING))?//Connect?to?DB ????????????????{ ????????????????????var?data?=?(from?c?in?_Courses ????????????????????????????????where?c.CourseID?==?ComboBox1.SelectedIndex ????????????????????????????????select?new?{?c.CourseDesc?} ????????????????????).FirstOrDefault();?//Select?CourseID?That?Corresponds?to?ComboBox?Selection ????????????????????TextBox1.Text?=?data.Name;?//Display ?????????????????}

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