Databases
StackOverflow2013
Postsdbo
PODynamic query in LINQ
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PODynamic query in LINQ
    primarykey
    data
    text
    <p>How do I write a dynamic query for Linq, if I have say Customer class which holds the fields:</p> <pre><code>string name string address int phoneno </code></pre> <p>I have to query based on information given similar to</p> <pre><code>query = string.Empty; if(!string.IsNullorEmpty(name)) { query += "@name = name"; } if(!string.IsNullorEmpty(address)) { query += "@address = address"; } if(!string.IsNullorEmpty(phoneno)) { query += "@phoneno = phoneno"; } var result = from condition in customer where(query) select condition; </code></pre> <p><strong>Edit #1:</strong> </p> <p>the items are changeable at run time like</p> <pre><code>private Customer[] GetCustomers(Dictionary&lt;string,string&gt; attributes) { here the attribute may be, name alone, or name and address, or name address and phoneno foreach(string field in attributes.key) { query += field == attributes[key]; } Customers[] =ExecuteQuery(query); } </code></pre> <p>Is this kind of query supported by LINQ?</p> <p><strong>Edit #2:</strong></p> <p>Hi Mouk,<br> As I am new to C#, I am still struggling, this is not working for me.</p> <pre><code>var query = _ConfigFile.ConnectionMasterSection; for(int i = 0; i &lt; filter.count; i++) { query = result.Where(p =&gt; typeof(ConnectionMaster).GetProperty(filter[i].Attribute).Name == filter[i].Value); } </code></pre> <p>This yeilds Empty, where as i used this</p> <pre><code>var query = _ConfigFile.ConnectionMasterSection; //Hard coded res.Where(q =&gt; q.category == filter[0].Value); </code></pre> <p>And it worked as I expected.</p> <p>Hi Bryan Watts,<br> I tried your code also and I getting this error: "Lambda Parameter not in scope".</p> <pre><code>for(int i = 0; i &lt; filter.count; i++) { Field item = filter[i]; MemberExpression param = Expression.MakeMemberAccess(Expression.Parameter(typeof(Connection), "p"), typeof(Connection).GetProperty(item.Attribute)); MemberExpression constant = Expression.MakeMemberAccess(Expression.Constant(item), typeof(Field).GetProperty("Value")); } try { var myquery = Queryable.Where(coll, Expression.Lambda&lt;Func&lt;Connection, bool&gt;&gt;( Expression.Equal(param, constant), Expression.Parameter(typeof(Connection),"p"))); } </code></pre> <p>What is the mistake here?</p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USQuintin Robinson
    1. This table or related slice is empty.
    plurals
    1. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. PODynamic query in LINQ
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PODynamic query in LINQ
      1. USMohanavel
      1. VTFavorite
    3. VO
      singulars
      1. PODynamic query in LINQ
      1. USBarbaros Alp
      1. VTFavorite
    1. COAdded an example to my answer which should guide you the rest of the way.
      singulars
      1. PODynamic query in LINQ
      1. USBryan Watts
 

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