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Binding ComboBox to DataTable (WinForms c#)?

I have a method which populates my ComboBox from a DataTable:
public string populateCompanyTransSellingEntityLookUp(ref System.Windows.Forms.ComboBox Combo, string Id, Contract Contract)
{
SqlCommand _comm = new SqlCommand();
_comm.Parameters.AddWithValue("#id", Id);
_comm.CommandText = "SELECT [name] FROM dbo.fnGetList(#id) ORDER BY [name]; ";
_comm.Connection = _conn;
_comm.CommandTimeout = _command_timeout;
DataTable dt = new DataTable();
try
{
SqlDataReader myReader = _comm.ExecuteReader();
dt.Load(myReader);
Combo.DataSource = dt;
Combo.DisplayMember = "name";
foreach (DataRow dr in dt.Rows)
{
if (dr["name"].ToString() == Contract.Company_Name.ToString())
{
Combo.Text = dr["company_int_name"].ToString();
}
}
}
catch
{
MessageBox.Show("Unable to populate Company Name LookUp");
}
return "";
}
I'm passing my saved value Contract.Company_Name into the forEach loop to find my required SelectedItem from the DataTable. The ComboBox is populated with my DataTable values from Combo.Datasource =dt; but my selected item isn't being set. The code compiles without exception. If I remove Datasource = dt;, theSelectedItemis set no problem. Why is theDatasourceoverriding mySelectedItem` and is there something I've missed with my binding?
Thanks all

At first you have to set the valueMember for sure. Then you can set the selectedValue Property instead of SelectedItem. The Item is one datasource record. So in your case it would be SelectedItem = dr! But iam not sure this is working.

Try this:
Combo.SelectedItem = dr;

I would suggest to use SelectedValue, then you don't need to loop through values "manually".
Also you don't need to use "heavy-weight" DataTable where you need just a collection of string values.
private IEnumerable<string> LoadNames(string id)
{
var query = "SELECT [name] FROM dbo.fnGetList(#id) ORDER BY [name]";
using (var connection = new SqlConnection("connectionString")
using (var command = new SqlCommand(query, connection)
{
// 36 is the size of the VarChar column in database(use your value)
command.Parameters.Add("#id", SqlDbType.VarChar, 36).Value = id;
connection.Open();
using (var reader = command.ExecuteReader())
{
var names = new List<string>();
while(reader.Read())
{
names.Add(reader.GetString(0));
}
return names;
}
}
}
public void Populate(ComboBox combobox, string id, Contract contract)
{
combobox.DataSource = LoadNames(id);
combobox.SelectedValue = contract.Copmpany_Name.ToString();
}
Few things to notice:
Dispose all objects which dealing with external resources (SqlConnection, SqlCommand and SqlDataReader)
Create SqlParameter with precise information about the type, for strings is important to provide size of the column in database. This information will improve SQL query performance on server side.
Don't pass combobox as a reference, populate method does not create new instance but only consume the given ComboBox instance.

Thank you for the help, I edited the code given that my problem was much more trivial.
public string populate_comboBox(ref System.Windows.Forms.ComboBox Combo)
{
SqlCommand _comm = new SqlCommand();
//edited for a simple one column sql query
_comm.CommandText ="SELECT [Column] FROM dbo.SQL_Table ORDER BY [Column];";
//MUST open sql connection to DB
SqlConnection conn = new SqlConnection(global_DB_String_Connection);
conn.Open();
_comm.Connection = conn;
DataTable dt = new DataTable();
try
{
SqlDataReader myReader = _comm.ExecuteReader();
dt.Load(myReader);
Combo.DataSource = dt;
Combo.DisplayMember = "ColumnName";
foreach (DataRow dr in dt.Rows)
{
//populates the combo box with query results
Combo.Text = dr["ColumnName"].ToString();
}
}
catch
{
Console.WriteLine("ComboBox Populate method has failed! ");
}
conn.Close();
return "";
}

About fetching data from datatable to gridviewin c#

I am trying to get column names for particular data table.
I tried with this code.
datagridFieldCreation.AutoGenerateColumns = false;
DataTable dt = new DataTable();
SqlDataAdapter sda = new SqlDataAdapter("select * from Add_Information ", con);
sda.Fill(dt);
datagridFieldCreation.DataSource = dt;
I am getting full data that is there in table. But I want only column names to be displayed one by one. Can any one help me out??

You can use ExecuteReader(CommandBehavior.SchemaOnly)):
DataTable schema = null;
using (var con = new SqlConnection(connection))
{
using (var schemaCommand = new SqlCommand("SELECT * FROM Add_Information", con))
{
con.Open();
using (var reader = schemaCommand.ExecuteReader(CommandBehavior.SchemaOnly))
{
schema = reader.GetSchemaTable();
}
}
}
datagridFieldCreation.DataSource = schema;
SchemaOnly:
The query returns column information only. When using SchemaOnly, the
.NET Framework Data Provider for SQL Server precedes the statement
being executed with SET FMTONLY ON.
The column name is in the first column of every row.
foreach (DataRow col in schema.Rows)
{
Console.WriteLine("ColumnName={0}", col.Field<String>("ColumnName"));
}
Adpated from: Using GetSchemaTable() to retrieve only column names

You can use:
SELECT * FROM YOURTABLENAME WHERE 0=1

Yes for sure, it is simple query which has a conditional statement which is always returning false, so each time you execute the query no rows will be extracted and only columns you will get so you can easily put up these columns in you DataGridView.

Is there easy method to read all tables from SQLite database to DataSet object?

Now I use method in C# to read table from SQLite database into DataTable,
but I want to send all table into other object.
So I think I have to use DataSet to combine all DataTable(s)
and send it to object as parameter.
Is there method that easy read all tables from SQLite database to DataSet?
Or I have to read all tables from SQLite database to DataTable each table
and combine to DataSet by hand?

The sql for listing all the tables is:
SELECT name FROM sqlite_master WHERE type = 'table' ORDER BY 1
you could then get all the tables as databases seperately and then add them into a dataset - an example here: http://www.dotnetperls.com/dataset
so i guess the code would be something like:
Dataset d = new Dataset()
foreach (tableName in GetTables()){
d.Tables.Add(GetDataTable("select * from "+tableName);
}
code for GetTables and GetDataTable (i'll leave the piecing it together to you):
public ArrayList GetTables()
{
ArrayList list = new ArrayList();
// executes query that select names of all tables in master table of the database
String query = "SELECT name FROM sqlite_master " +
"WHERE type = 'table'" +
"ORDER BY 1";
try
{
DataTable table = GetDataTable(query);
// Return all table names in the ArrayList
foreach (DataRow row in table.Rows)
{
list.Add(row.ItemArray[0].ToString());
}
}
catch (Exception e)
{
Console.WriteLine(e.Message);
}
return list;
}
public DataTable GetDataTable(string sql)
{
try
{
DataTable dt = new DataTable();
using (var c = new SQLiteConnection(dbConnection))
{
c.Open();
using (SQLiteCommand cmd = new SQLiteCommand(sql, c))
{
using (SQLiteDataReader rdr = cmd.ExecuteReader())
{
dt.Load(rdr);
return dt;
}
}
}
}
catch (Exception e)
{
Console.WriteLine(e.Message);
return null;
}
}

Finding unique rows in SQL Server Table

I'm looking at the example here:
http://msdn.microsoft.com/en-US/library/y06xa2h1(v=vs.80).aspx
string s = "primaryKeyValue";
DataRow foundRow = dataSet1.Tables["AnyTable"].Rows.Find(s);
if (foundRow != null)
{
MessageBox.Show(foundRow[1].ToString());
}
else
{
MessageBox.Show("A row with the primary key of " + s + " could not be found");
}
They don't specify where does dataSet1 come from and does this represent some database?
I'm trying to use this example in my code to find unique rows but I can't seem to implement this syntax. I'm only using connection string to open connection to SQL and I use SqlDataAdapter to perform functions...
EDIT:
SqlConnection myConnection = new SqlConnection("Data Source=server; Initial Catalog=Dashboard; Integrated Security=SSPI; Persist Security Info=false; Trusted_Connection=Yes");
SqlDataAdapter da = new SqlDataAdapter();
try
{
//Opens the connection to the specified database
myConnection.Open();
//Specifies where the Table in the database where the data will be entered and the columns used
da.InsertCommand = new SqlCommand("INSERT INTO DashboardLibAnswer(Id,Date,Time,Question,Details,Answer,Notes,EnteredBy,WhereReceived,QuestionType,AnswerMethod,TransactionDuration)"
+ "VALUES(#Id,#Date,#Time,#Question,#Details,#Answer,#Notes,#EnteredBy,#WhereReceived,#QuestionType,#AnswerMethod,#TransactionDuration)", myConnection);
//Specifies the columns and their variable type where the data will be entered
//Special note: Conversion from String > DateTime will cause exceptions that will only import some part of data and not everything
da.InsertCommand.Parameters.Add("#Id", SqlDbType.NVarChar);
da.InsertCommand.Parameters.Add("#Date", SqlDbType.Text);
da.InsertCommand.Parameters.Add("#Time", SqlDbType.Text);
da.InsertCommand.Parameters.Add("#Question", SqlDbType.Text);
da.InsertCommand.Parameters.Add("#Details", SqlDbType.Text);
da.InsertCommand.Parameters.Add("#Answer", SqlDbType.Text);
da.InsertCommand.Parameters.Add("#Notes", SqlDbType.Text);
da.InsertCommand.Parameters.Add("#EnteredBy", SqlDbType.NVarChar);
da.InsertCommand.Parameters.Add("#WhereReceived", SqlDbType.NVarChar);
da.InsertCommand.Parameters.Add("#QuestionType", SqlDbType.NVarChar);
da.InsertCommand.Parameters.Add("#AnswerMethod", SqlDbType.NVarChar);
da.InsertCommand.Parameters.Add("#TransactionDuration", SqlDbType.NVarChar);
//Using the global variable counter this loop will go through each valid entry and insert it into the specifed database/table
for (int i = 0; i < counter; i++)
{
//Iterates through the collection array starting at first index and going through until the end
//and inserting each element into our SQL Table
DataSet dashboardDS = new DataSet();
da.Fill(dashboardDS, "DashboardLibAnswer");
DataTable dt = dashboardDS.Tables["DashboardLibAnswer"];
foreach (DataColumn col in dt.Columns)
{
if (col.Unique)
{
da.InsertCommand.Parameters["#Id"].Value = collection.getIdItems(i);
da.InsertCommand.Parameters["#Date"].Value = collection.getDateItems(i);
da.InsertCommand.Parameters["#Time"].Value = collection.getTimeItems(i);
da.InsertCommand.Parameters["#Question"].Value = collection.getQuestionItems(i);
da.InsertCommand.Parameters["#Details"].Value = collection.getDetailsItems(i);
da.InsertCommand.Parameters["#Answer"].Value = collection.getAnswerItems(i);
da.InsertCommand.Parameters["#Notes"].Value = collection.getNotesItems(i);
da.InsertCommand.Parameters["#EnteredBy"].Value = collection.getEnteredByItems(i);
da.InsertCommand.Parameters["#WhereReceived"].Value = collection.getWhereItems(i);
da.InsertCommand.Parameters["#QuestionType"].Value = collection.getQuestionTypeItems(i);
da.InsertCommand.Parameters["#AnswerMethod"].Value = collection.getAnswerMethodItems(i);
da.InsertCommand.Parameters["#TransactionDuration"].Value = collection.getTransactionItems(i);
da.InsertCommand.ExecuteNonQuery();
}
}
//Updates the progress bar using the i in addition to 1
_worker.ReportProgress(i + 1);
} // end for
//Once the importing is done it will show the appropriate message
MessageBox.Show("Finished Importing");
} // end try
catch (Exception exceptionError)
{
//To show exceptions thrown just uncomment bellow line
//rtbOutput.AppendText(exceptionError.ToString);
} // end catch
//Closes the SQL connection after importing is done
myConnection.Close();
}

if you populate a dataset from your data adapter, you'll be able to follow the same logic -
http://msdn.microsoft.com/en-us/library/bh8kx08z(v=vs.71).aspx
It might be worth showing what you actually have to get more specific help
EDIT
I think I'm understanding what you want - if you fill your datatable from the already populated table, just check the item doesn't already exist before adding it - i.e.
if (dt.Rows.Find(collection.getIdItems(i)) == null)
{
// add your new row
}
(just to be sure I knocked together a quick test - hopefully this helps):
// MyContacts db has a table Person with primary key (ID) - 3 rows - IDs 4,5,6
SqlConnection myConnection = new SqlConnection("Data Source=.; Initial Catalog=MyContacts; Integrated Security=SSPI; Persist Security Info=false; Trusted_Connection=Yes");
SqlDataAdapter da = new SqlDataAdapter();
da.SelectCommand = new SqlCommand("select * from Person", myConnection);
myConnection.Open();
DataSet dashboardDS = new DataSet();
da.Fill(dashboardDS, "Person");
dashboardDS.Tables[0].PrimaryKey = new[] { dashboardDS.Tables[0].Columns["ID"]};
List<int> ids = new List<int> {4, 6, 7};
foreach (var id in ids)
{
if (dashboardDS.Tables[0].Rows.Find(id) == null)
{
Console.WriteLine("id not in database {0}", id); //i.e. 7
}
}

You will first need to open a connection to your database. This is an excellent source for connection strings: The Connection String Reference.
Then you will need to fill the dataset with data from some table. Since we are only interested in the schema information we are only selecting one row (SELECT TOP 1 ...).
Then we can go through the columns and check their Unique property (Boolean):
string connString =
"server=(local)\\SQLEXPRESS;database=MyDatabase;Integrated Security=SSPI";
string sql = #"SELECT TOP 1 * FROM AnyTable";
using (SqlConnection conn = new SqlConnection(connString)) {
conn.Open();
SqlDataAdapter da = new SqlDataAdapter(sql, conn);
using (DataSet ds = new DataSet()) {
da.Fill(ds, "AnyTable");
DataTable dt = ds.Tables["AnyTable"];
foreach (DataColumn col in dt.Columns) {
if (col.Unique) {
Console.WriteLine("Column {0} is unique.", col.ColumnName);
}
}
}
}
UPDATE #1
Sorry, I missunderstood your question. The above example returns unique columns, not unique rows. You can get unique (distinct) rows by using the DISTINCT keyword in SQL:
SELECT DISTINCT field1, field2, field3 FROM AnyTable
You can then fill the data table the same way as above.
Usually the word "unique" is used for unique constraints and unique indexes in database jargon. The term "distinct" is used for rows which are different.
UPDATE #2
Your updated question seems to suggest that you don't want find unique rows, but that you want to insert unique rows (which is the exact opposite).
Usually you would select distinct items from a collection like this. However it is difficult to answer your question accurately, since we don't know the type of your collection.
foreach (var item in collection.Distinct()) {
}
UPDATE #3
The easiest way to insert distinct values in the SQL Server table is to filter the rows at their origin, when reading them from the CSV-File; even before splitting them.
string[] lines = File.ReadAllLines(#"C:\Data\MyData.csv");
string[][] splittedLines = lines
.Distinct()
.Select(s => s.Split(','))
.ToArray();
Now you have distinct (unique) splitted lines that you can insert into the SQL Server table.

store select result

i want to extract my table names and save it into variables this is my cod that return 3 answer:student, teacher and score. how can i change it to save these tree table name to 3 variable. thank you.
try
{
SqlDataReader myreader = null;
SqlCommand mycommand = new SqlCommand("select * FROM information_schema.tables WHERE table_type = 'BASE TABLE'", myconnect);
myreader = mycommand.ExecuteReader();
while (myreader.Read())
{
Console.WriteLine(myreader[2].ToString());
}
}

A simple builtin way is using Connection.GetSchema:
using (var con = new System.Data.SqlClient.SqlConnection(conStr))
{
con.Open();
DataTable schemaTable = con.GetSchema("Tables");
IList<string> allTableNames = schemaTable.AsEnumerable()
.Where(r => r.Field<string>("TABLE_TYPE") == "BASE TABLE")
.Select(r => r.Field<string>("TABLE_NAME"))
.ToList();
}
Now you have a List<string> with all table names which you can access via indexer or in a loop or create a comma separated list with string.Join:
string tNames = string.Join(",", allTableNames);
Console.Write("all tables in the given database: " + tNames);

You can use this :
string tableName ="" ; // Variable to stroe the table names
string connectionString = ""; //Your connectionstring
// get records from the table
string commandString =""; //Your query
// create the data set command object
// and the DataSet
SqlDataAdapter DataAdapter =new SqlDataAdapter(commandString, connectionString);
DataSet DataSet = new DataSet( );
// fill the DataSet object
DataAdapter.Fill(DataSet, "Customers");
// Get the one table from the DataSet
DataTable dataTable = DataSet.Tables[0];
// for each row in the table, display the info
foreach (DataRow dataRow in dataTable.Rows)
{
tableName = dataRow[0].tostring();
//...
}

if you want to save the result for future user or a different session then you can use any of the following to methods
first one
use the "insert" query to save the result one by one in the a different table that you would create specially for saving the data
you can put the insert command/statement directly into the for loop
second method
use the xml to store the value very simple and memory friendly

I Have modified #Doctor code to use ArrayList to store number of table name in single variables.
ArrayList alTableName = new ArrayList(); // Variable to stroe the table names
string connectionString = ""; //Your connectionstring
// get records from the table
string commandString =""; //Your query
// create the data set command object
// and the DataSet
SqlDataAdapter DataAdapter =new SqlDataAdapter(commandString, connectionString);
DataSet DataSet = new DataSet( );
// fill the DataSet object
DataAdapter.Fill(DataSet, "Customers");
// Get the one table from the DataSet
DataTable dataTable = DataSet.Tables[0];
// for each row in the table, display the info
foreach (DataRow dataRow in dataTable.Rows)
{
alTableName.Add(dataRow[0].tostring());
//...
}