i have a form with a collection of about five drop down . i have my query as follows .
string sql = "SELECT a.clientID ,a.[cname],b.bid,b.[bname],c.contactID, c.[name] FROM "
+ " dbo.[CLIENT] AS a INNER JOIN dbo.[BRANCH] AS b "
+ "ON a.clientID = b.clientID JOIN dbo.[CONTACT] AS "
+ " c ON b.bid = c.bid ORDER BY a.clientID ";
i then followed and bind my drop down individually to their respective columns as follows.
SqlCommand cmd = new SqlCommand(sql, connection);
cmd.CommandType = CommandType.Text;
SqlDataReader reader = cmd.ExecuteReader();
drClient.Enabled = true;
drClient.DataSource = reader;
drClient.DataTextField = "cname";
drClient.DataValueField = "clientID";
drClient.DataBind();
drBranch.Enabled = true;
drBranch.DataSource = reader;
drBranch.DataTextField = "bname";
drBranch.DataValueField = "bid";
drBranch.DataBind();
drContact.Enabled = true;
drContact.DataSource = reader;
drContact.DataTextField = "name";
drContact.DataValueField = "contactID";
drContact.DataBind();
drEmail.Enabled = true;
drEmail.DataSource = reader;
drEmail.DataTextField = "name";
drEmail.DataValueField = "contactID";
drEmail.DataBind();
drFax.Enabled = true;
drFax.DataSource = reader;
drFax.DataValueField = "contactID";
drFax.DataTextField = "name";
drFax.DataBind();
when i run this, only the first drop down bind successfully. The rest don't. I also try to loop through the reader by adding
while(reader.read())
{
then my bindings
}
the above also fails. I though of looping as below as well.
while(read.HasRows)
{
}
it still fails. I am confused,any help would be appreciated. thanks
Reader is readonly and forward only that's why only first dropdonw get filled with data and others are empty.
You can use datset or Datatable for same problem .
SqlCommand cmd = new SqlCommand(sql, connection);
cmd.CommandType = CommandType.Text;
Dataset dsresult = cmd.ExecuteDataset();
If(dsResult !=null)
{
if(dsResult.Rows.count>0)
{
drClient.Enabled = true;
drClient.DataSource = dsResult.Tables[0] ;
drClient.DataTextField = Convert.ToString(ds.Tables[0].Columns["cname"]);
drClient.DataValueField = ds.Tables[0].Columns["clientID"] ;
drClient.DataBind();
}
}
Datareader is connected architecture needs continuous connection and fetches one row at a time in forward mode better use dataset which uses disconnected architecture and can be used for retrieving data multiple times.
This seems clear postback problem.
Bind your drop down on !postback.
Eg.
if(!IsPostBack)
{
populateDdl();
}
Either you will have to make a seperate reader for each binding
or you can do this by filling a datatable ( i would prefer this). Like,
DataTable dt = new DataTable();
using (SqlDataAdapter a = new SqlDataAdapter(sql, connection))
{
a.Fill(dt);
}
drClient.DataSource = dt;
drClient.DataBind();
drBranch.DataSource = dt;
drBranch.DataBind();
drContact.DataSource = dt;
drContact.DataBind();
drFax.DataSource = dt;
drFax.DataBind();
Your choices are to either rerun/refill it or create separate readers or better yet fill a datatable instead and then you can reuse the datatable.
Related
I am trying to drop down box in design but in database table category has duplicates. I tried to execute by using below code. But it is not executing. It just receiving all commands which I have been changes in properties:
cmd.CommandText = #"Select Distinct Category_Desc from
Database***name order
by Category_Desc";
adapter.SelectCommand = cmd;
SqlDataReader dr1 = cmd.ExecuteReader();
dr1.Read();
comboBoxCategory.ValueMember = "Category_Desc";
comboBoxCategory.DisplayMember = "Category_Desc";
comboBoxCategory.DataSource = dr1;
dr1.Dispose();
Can anyone please help how to execute distinct query from the code?
Data reader is a forward only cursor that you have to iterate and close after the last item.Look at this code segment
SqlDataReader dr1= command.ExecuteReader();
ArrayList arl= new ArrayList();
while (dr1.Read())
{
arl.Add(dr1("Category_Desc"));
}
dr1.close();
//If its a winform project use this
string [] str = al.ToArray(typeof(string));
FarPoint.Win.Spread.ComboBoxCellType cb = new
FarPoint.Win.Spread.ComboBoxCellType();
cb.Items = arl;
Use the adapter to fill a DataTable instead. You already have the adapter and it already has the SelectCommand assigned.
adapter.SelectCommand = cmd;
System.Data.DataTable dtCategories = new System.Data.DataTable();
adapter.Fill(dtCategories);
comboBoxCategory.ValueMember = "Category_Desc";
comboBoxCategory.DisplayMember = "Category_Desc";
comboBoxCategory.DataSource = dtCategories;
I have a program that will retrieve student and class information.
I already use if (!reader.HasRows) to check if the student is existing but the problem is not all student is already registered in a certain class and I want it continue retrieving data even the values in the class information is Null. I am new to C# and any help and recommendation is deeply appreciated.
private void btnstudsearch_Click_1(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection(#"data source = DELL-USER\SQLEXPRESS;integrated security = SSPI;database = Enrollment System");
DataTable dt = new DataTable();
con.Open();
SqlDataReader reader = null;
SqlCommand cmd = new SqlCommand("select tbl_studregs.fname, tbl_studregs.mname, tbl_studregs.lname, tbl_studregs.age, tbl_studregs.sex,
tbl_studregs.address, tbl_studregs.gname, tbl_studregs.gcnum, tbl_studregs.educlevel, tbl_class.yglevel, tbl_class.section from tbl_studregs
inner join tbl_class on tbl_studregs.classid = tbl_class.classid where tbl_studregs.studid = #id ", con);
cmd.Parameters.AddWithValue("#id", txtstudsearch.Text);
reader = cmd.ExecuteReader();
if (!reader.HasRows)
{
MessageBox.Show("Student not found! Please recheck the student ID!", "", MessageBoxButtons.OK, MessageBoxIcon.Information);
ClearAllTextBox();
}
else
{
while (reader.Read())
{
txtstudfname.Text = reader.GetValue(0).ToString();
txtmname.Text = reader.GetValue(1).ToString();
txtstudlname.Text = reader.GetValue(2).ToString();
txtage.Text = reader.GetValue(3).ToString();
cboxsex.Text = reader.GetValue(4).ToString();
rtxtaddress.Text = reader.GetValue(5).ToString();
txtgname.Text = reader.GetValue(6).ToString();
txtgcnum.Text = reader.GetValue(7).ToString();
cboxstudlevel.Text = reader.GetValue(8).ToString();
txtstudyearlev.Text = reader.GetValue(9).ToString();
txtstudsec.Text = reader.GetValue(10).ToString();
}
}
}
If I understand correctly, you want to retrieve the information for a student even if there isn't a class connected to them on the tbl_class table. I think it would help most you to look up the difference between different SQL join operations.
It looks like what you want is a left join instead of an inner join in your SQL query, although it may depend on what your database looks like.
Is there a way to map the results of a stored procedure to a generic list instead of a dataset/datatable?
Currently I follow these steps:
Execute stored procedure
Take the result in Dataset
Populate list from the Dataset.
Is there a way to eliminate step (2).
OleDbCommand cm = new OleDbCommand();
cm.Connection = AccessConnection();
cm.CommandType = CommandType.StoredProcedure;
cm.CommandText = "seltblContacts";
OleDbDataAdapter adp = new OleDbDataAdapter(cm);
DataTable dt = new DataTable();
adp.Fill(dt);
List<tblContacts> LstFile = new List<tblContacts>();
if (dt.Rows.Count > 0)
{
tblContacts t;
foreach (DataRow dr in dt.Rows)
{
t = PopulateContacts(dr);
LstFile.Add(t);
}
}
Yes of course you can do that - just execute your command and get back a reader, and then iterate over the rows in the result set and build up your objects:
using (OleDbCommand cm = new OleDbCommand())
{
cm.Connection = AccessConnection();
cm.CommandType = CommandType.StoredProcedure;
cm.CommandText = "seltblContacts";
List<tblContacts> LstFile = new List<tblContacts>();
using (OleDbReader reader = cm.ExecuteReader())
{
while(reader.Read())
{
tblContacts contact = new tblContacts();
// here, set the properties based on your columns from the database
contact.FirstName = reader.GetString(0);
contact.LastName = reader.GetString(1);
// etc.
LstFile.Add(contact);
}
reader.Close();
}
return LstFile;
}
For details on OleDbReader and how to use it, see this other SO question or find tons of tutorials and samples online using Bing or Google.
I'm using Visual Studio 2010 and C# to create a windows form with a combobox that should contain employees initials. I have spent the last few days searching through every solution I can find and I still can not get my combobox to populate.
This is what I've got as of now:
public static void FillComboBox(string Query, System.Windows.Forms.ComboBox LoggedByBox)
{
using (var CONN = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\\Users\\Documents\\Service Request Application\\bin\\Debug\\servicereq1.mdb"))
{
CONN.Open();
DataTable dt = new DataTable();
try
{
OleDbCommand cmd = new OleDbCommand(Query, CONN);
OleDbDataReader myReader = cmd.ExecuteReader();
dt.Load(myReader);
}
catch (OleDbException e)
{
Console.WriteLine(e.ToString());
Console.ReadLine();
return;
}
LoggedByBox.DataSource = dt;
LoggedByBox.ValueMember = "ID";
LoggedByBox.DisplayMember = "Initials";
}
}
Then I call it when the form loads
private void Form1_Load(object sender, EventArgs e)
{
FillComboBox("select ID, Initials from [Fixers and Testers]", LoggedByBox);
}
When I run the program, the combobox is still blank. I'm positive that my column names and table names are correct. Any suggestions?
I finally got my ComboBox filled and I wanted to share what I changed for anyone else who stumbles across this question in their searches. After spending a bit more time searching through other questions and MSDN, I was able to come up with this.
private void LoadComboLogged()
{
AppDomain.CurrentDomain.SetData("DataDirectory",#"\\prod\ServiceRequests");
string strCon = #"Provider=Microsoft.Jet.OLEDB.4.0;DataSource=|DataDirectory|\servicereq1.mdb";
try
{
using (OleDbConnection conn = new OleDbConnection(strCon))
{
conn.Open();
string strSql = "SELECT Initials FROM [Fixers and Testers] WHERE [Status] ='C'";
OleDbDataAdapter adapter = new OleDbDataAdapter(new OleDbCommand(strSql, conn));
DataSet ds = new DataSet();
adapter.Fill(ds);
loggedByComboBox.DataSource = ds.Tables[0];
loggedByComboBox.DisplayMember = "Initials";
loggedByComboBox.ValueMember = "Initials";
}
}
catch (Exception ex)
{
}
}
I also found that I needed to call
LoadComboLogged();
when I initialized my form. Without that line, the ComboBox would only show a blank dropdown list. Hope this helps someone else who runs into this problem.
Passing control to static method causing this issue. Instead of passing control to the method make that method returns the table and within the load method load the control.
SqlConnection con = new SqlConnection("Data Source=RUSH-PC\\RUSH;Initial Catalog=Att;Integrated Security=True");
con.Open();
SqlDataAdapter da = new SqlDataAdapter("select name from userinfo", con);
DataTable dt = new DataTable();
da.Fill(dt);
DataRow dr;
dr = dt.NewRow();
dt.Rows.InsertAt(dr, 1);
comboBox1.DisplayMember = "name";
comboBox1.ValueMember = "name";
comboBox1.DataSource = dt;
con.Close();
This may help you...
Good luck...:-)
Another possible solution would be to query and return a list of strings. Perhaps it may be less efficient, but it's what I used in a recent project of mine. Here's an example that would reside in a method, possibly called GetInitialsFromDatabase():
using(var conn = new MySqlConnection(connectionString)
{
conn.Open();
using(MySqlCommand cmd = new MySqlCommand())
{
cmd.Connection = conn;
cmd.CommandText = "SELECT Initials FROM [Fixers and Testers] WHERE [Status] ='C'";
MySqlDataReader reader = cmd.ExecuteReader();
while(reader.Read())
{
// initials is a List<String> previously defined (Assuming strings)
initials.Add(String.Format("{0}", reader[0]));
}
}
conn.Close();
}
And then return the initials List, and then in your GUI you could say:
comboBox1.DataSource = returnedList;
comboBox1.DropDownStyle = ComboBoxStyle.DropDownList;
I would like to make one call (containing several SELECT statement) to the database and then databind the results to multiple components.
I'm using a DataSet and SqlDataAdapter to fill tables that are then bound to components.
Problem is the results of the first SELECT statement are put into both tables so I get a "'System.Data.DataRowView' does not contain a property..." error when I try to use the second lot of data on the second component.
Have I misunderstood how this is meant to work?
DataSet ds = new DataSet();
SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["myString"].ConnectionString);
StringBuilder topicDropDownListSQL = new StringBuilder();
topicDropDownListSQL.Append("SELECT topic.topic_ID, topic.topic_title FROM FPL2012_TOPIC as topic WHERE topic.topic_isEnabled = 1;");
topicDropDownListSQL.Append("SELECT explain.itemExplanationType_ID, explain.itemExplanationType_type FROM FPL2012_ITEM_EXPLANATION_TYPE as explain;");
SqlDataAdapter da = new SqlDataAdapter(topicDropDownListSQL.ToString(), connection);
ds.Tables.Add("Topics");
ds.Tables.Add("ExplainType");
ds.EnforceConstraints = false;
ds.Tables["Topics"].BeginLoadData();
da.Fill(ds.Tables[0]);
ds.Tables["Topics"].EndLoadData();
ds.Tables["ExplainType"].BeginLoadData();
da.Fill(ds.Tables[1]);
ds.Tables["ExplainType"].EndLoadData();
topicDropDownList.DataValueField = "topic_ID";
topicDropDownList.DataTextField = "topic_title";
topicDropDownList.DataSource = ds.Tables["Topics"];
topicDropDownList.DataBind();
explanationTypeDropDownList.DataValueField = "itemExplanationType_ID";
explanationTypeDropDownList.DataTextField = "itemExplanationType_type";
explanationTypeDropDownList.DataSource = ds.Tables["ExplainType"];
explanationTypeDropDownList.DataBind();
connection.Close();
You can use this acces the tables by there indexes not by there names
DataSet ds = new DataSet();
SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["myString"].ConnectionString);
String qry="SELECT topic_ID,topic_title FROM FPL2012_TOPIC WHERE topic_isEnabled = 1; SELECT itemExplanationType_ID, itemExplanationType_type FROM FPL2012_ITEM_EXPLANATION_TYPE ";
SqlDataAdapter da = new SqlDataAdapter(qry, connection);
da.Fill(ds)
topicDropDownList.DataValueField = "topic_ID";
topicDropDownList.DataTextField = "topic_title";
topicDropDownList.DataSource = ds.Tables[0];
topicDropDownList.DataBind();
explanationTypeDropDownList.DataValueField = "itemExplanationType_ID";
explanationTypeDropDownList.DataTextField = "itemExplanationType_type";
explanationTypeDropDownList.DataSource = ds.Tables[1];
explanationTypeDropDownList.DataBind();
connection.Close();
OK, I tried using a datareader next, didn't expect it to work but it does! I can make multiple select statements and then fill multiple componenets. I'm not marking this as an answer as I still think it would be useful to know how to do it using the dataset.
The new code that worked for me (in case it is useful):
string connectionString = WebConfigurationManager.ConnectionStrings["myString"].ConnectionString;
SqlConnection connection = new SqlConnection(connectionString);
StringBuilder sql = new StringBuilder();
sql.Append("SELECT topic.topic_ID, topic.topic_title FROM FPL2012_TOPIC as topic WHERE topic.topic_isEnabled = 1;");
sql.Append("SELECT explain.itemExplanationType_ID, explain.itemExplanationType_type FROM FPL2012_ITEM_EXPLANATION_TYPE as explain;");
SqlCommand command = new SqlCommand(sql.ToString(), connection);
connection.Open();
SqlDataReader reader = command.ExecuteReader();
topicDropDownList.DataSource = reader;
topicDropDownList.DataValueField = "topic_ID";
topicDropDownList.DataTextField = "topic_title";
topicDropDownList.DataBind();
reader.NextResult();
explanationTypeDropDownList.DataSource = reader;
explanationTypeDropDownList.DataValueField = "itemExplanationType_ID";
explanationTypeDropDownList.DataTextField = "itemExplanationType_type";
explanationTypeDropDownList.DataBind();
reader.Close();
connection.Close();