20140911 multi-condition Query

Using system;
Using system. Collections. Generic;
Using system. componentmodel;
Using system. Data;
Using system. drawing;
Using system. LINQ;
Using system. text;
Using system. Threading. tasks;
Using system. Windows. forms;
Using system. Data. sqlclient;

Namespace multi-condition Query
{
Public partial class form1: Form
{
Public form1 ()
{
Initializecomponent ();
}

Private void form1_load (Object sender, eventargs E)
{
Bands ();
}

Private void bands ()
{
String SQL = "select CID, cname, CDESC from tclass ";
Datatable dt = sqlhelper. gettable (SQL );
Datagridview1.datasource = DT;
}

Private void btncha_click (Object sender, eventargs E)
{
String SQL = "select CID, cname, CDESC from tclass where 1 = 1 ";
List <sqlparameter> List = new list <sqlparameter> ();
If (! String. isnullorempty (txtname. Text ))
{
SQL + = "and cname like @ cname ";
List. Add (New sqlparameter ("@ cname", "%" + txtname. Text + "% "));
}
If (! String. isnullorempty (txtinfo. Text ))
{
SQL + = "and CDESC like @ CDESC ";
List. Add (New sqlparameter ("@ CDESC", "%" + txtinfo. Text + "% "));
}
Sqldatareader DR = sqlhelper. executereader (SQL, list. toarray ());
List <class> listn = new list <class> ();
If (dr. hasrows)
{
While (dr. Read ())
{
Class C = new class ();
C. CDESC = Dr ["CDESC"]. tostring ();
C. cname = Dr ["cname"]. tostring ();
C. cid = convert. toint32 (Dr ["CID"]);
Listn. Add (C );
}
}
Datagridview1.datasource = listn;

}
}
}

 

 

For example, I can only perform step-by-step query on Fuzzy queries with multiple columns during the first query. I used or, but the concatenated string is too large (there are 10 column names)

The four method resource managers encapsulated by dataset sqlhelper and the multi-condition query above are learned today.

After several days of ADO learning, I gradually began to understand the role of the entity class. Each table corresponds to an entity class.

For the first time, I felt that my life was full of pressure. Although I was just moving towards this threshold, I can stick to it!

A cainiao. I am studying hard!

 

Resource Manager

Using system;
Using system. Collections. Generic;
Using system. componentmodel;
Using system. Data;
Using system. drawing;
Using system. LINQ;
Using system. text;
Using system. Threading. tasks;
Using system. Windows. forms;
Using system. Data. sqlclient;

Namespace Resource Manager
{
Public partial class form1: Form
{
Public form1 ()
{
Initializecomponent ();
}

Private void form1_load (Object sender, eventargs E)
{
// Obtain the heel Element
List <Category> List = GETID (-1 );
// Add the element to the node
Loadnodes (list, TV. nodes );

}

Private void loadnodes (list <Category> list, treenodecollection TNC)
{
Foreach (Category item in List)
{
Treenode Tn = TNC. Add (item. tname );
Tn. Tag = item. TID;
// Recursively traverse all the information in it
Loadnodes (GETID (item. TID), TN. nodes );

}
}

Private list <Category> GETID (int p)
{
List <Category> List = new list <Category> ();
String SQL = "select tid, tname from category where tparentid =" + P;
Sqldatareader DR = sqlhelper. executereader (SQL );

CATEGORY cat = NULL;
If (dr. hasrows)
{
While (dr. Read ())
{
Cat = new category ();
Cat. tid = convert. toint32 (Dr ["TID"]);
Cat. tname = Dr ["tname"]. tostring ();
// Cat. tparentid = convert. toint32 (Dr ["tparentid"]);
List. Add (CAT );
}
}
Return list;
}

Private void TV _afterselect (Object sender, treevieweventargs E)
{
// MessageBox. Show (TV. selectednode. Tag. tostring ());
If (TV. selectednode. Tag! = NULL) // get the TID that was just stored on it
{
Int id = convert. toint32 (TV. selectednode. Tag );
Getbyid (ID );

}
}

Private void getbyid (int id)
{
List <contentinfo> List = new list <contentinfo> ();
String SQL = "select did, dtid, dname, DContent from contentinfo where dtid =" + ID;
Sqldatareader DR = sqlhelper. executereader (SQL );
If (dr. hasrows)
{
While (dr. Read ())
{
Contentinfo Cn = new contentinfo ();
// CN. DContent = Dr ["DContent"]. tostring ();
CN. Did = convert. toint32 (Dr ["did"]);
CN. dname = Dr ["dname"]. tostring ();
List. Add (CN );
}
}
Listbox1.datasource = List;
Listbox1.displaymember = "dname ";
Listbox1.valuemember = "did ";

}

Private void listbox1_selectedindexchanged (Object sender, eventargs E)
{
If (listbox1.selecteditems. Count> 0)
{
// MessageBox. Show (listbox1.selectedvalue. tostring ());
String id = listbox1.selectedvalue. tostring ();

String SQL = "select DContent from contentinfo Where did =" + ID;
Sqldatareader DR = sqlhelper. executereader (SQL );
Contentinfo Cn = new contentinfo ();
If (dr. hasrows)
{
While (dr. Read ())
{

CN. DContent = Dr ["DContent"]. tostring ();
}
Textbox1.text = cn. DContent;
}
}
}
}
}

This is because I just learned a little bit difficult to do. Alas, people are a little stupid and can only make up for it by diligence!

20140911 multi-condition Query