LINQ to Entities多条件动态查询实现

using (testContext context = new testContext())
{
    var query = context.Users.AsQueryable();

    //动态查询
    string usn = Request.Form["usn"];
    if (usn != null)
        query = query.Where(u => u.usn == usn);
    string ww = Request.Form["ww"];
    if (ww != null)
        query = query.Where(u => u.wangwang == ww);

    Label1.Text = query.Select(u => u.id).First().ToString();
}

exec sp_executesql N'Select TOP (1) 
[Extent1].[id] AS [id]
FROM [dbo].[User] AS [Extent1]
Where ([Extent1].[usn] = @p__linq__0) AND ([Extent1].[wangwang] = @p__linq__1)',N'@p__linq__0 nvarchar(4000),@p__linq__1 nvarchar(4000)',@p__linq__0=N'dnawo',@p__linq__1=N'abc'

using (testContext context = new testContext())
{
    var query = context.Users[color=red].ToList()[/color];

    //动态查询
    string usn = Request.Form["usn"];
    if (usn != null)
        query = query.Where(u => u.usn == usn)[color=red].ToList()[/color];
    string ww = Request.Form["ww"];
    if (ww != null)
        query = query.Where(u => u.wangwang == ww)[color=red].ToList()[/color];

    Label1.Text = query.Select(u => u.id).First().ToString();
}