Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>I've done something similiar to this in a project recently. What I ended up doing was implementing the repository pattern and created a method on the repository called "ApplyFilter" which looked something like:</p> <pre><code>void ApplyFilter(Expression&lt;Func&lt;TEntity, bool&gt;&gt; predicate) { if(this.resultSet == null) { this.resultSet = this.context.Set&lt;TEntity&gt;().AsQueryable(); } this.resultSet = this.resultSet.Where(predicate); } </code></pre> <p>And had a property on my repository called "ResultSet" which just returned the IQueryable&lt;TEntity&gt; resultSet field and forced an enumeration of the results (triggering EF's database call). This way I could apply all the dynamically created expressions in a clean why before enumerating the results.</p> <p>The real difference between what my code does and what yours is doing is my code appends the boolean predicate to the final Expression tree where as you are trying to use yours within the final expression tree. My way basically creates/appends a WHERE clause to the SQL, yours tries to generate a SQL function call from the "DatesBetween" method.</p> <p>Here is something to try:</p> <pre><code> public static Expression&lt;Func&lt;TEntity, bool&gt;&gt; MakeDateRange&lt;TEntity&gt;(DateTime? dateFrom, DateTime? dateTo) { var et = typeof(TEntity); var param = Expression.Parameter(et, "a"); var prop = et.GetProperty("UpdatedDate"); Expression body = null, left = null, right = null; if (prop == null) { prop = et.GetProperty("CreatedDate"); if (prop == null) { prop = et.GetProperty("Date"); } } if (dateFrom.HasValue) { left = Expression.GreaterThanOrEqual(Expression.PropertyOrField(param, prop.Name), Expression.Constant(dateFrom.GetValueOrDefault())); } if (dateTo.HasValue) { right = Expression.LessThanOrEqual(Expression.PropertyOrField(param, prop.Name), Expression.Constant(dateTo.GetValueOrDefault())); } if (left != null &amp;&amp; right != null) { body = Expression.AndAlso(left, right); } else if (left != null) { body = left; } else { body = right; } return Expression.Lambda&lt;Func&lt;TEntity, bool&gt;&gt;(body, param); } </code></pre>
    singulars
    1. This table or related slice is empty.
    1. POFiltering Entity Framework results on SQL Server
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USdoogle
    1. USdoogle
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POFiltering Entity Framework results on SQL Server
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTAcceptedByOriginator
    1. COI'm ok with changing the implementation. I'm trying to use my `DatesBetween` method to build the SQL. The problem is my predicate is way more complicated than normal, because it's conditional based on what properties do or don't exist. I haven't been able to come up with a way to genericize that decision without EF freaking out about it.
      singulars
      1. PO
      1. USBryan Boettcher
    2. COI've added a code block in my answer with a possible method that could solve your problem. It checks for the existence of properties on the type using reflection.
      singulars
      1. PO
      1. USdoogle
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload