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Output data from DataTables within DataSet

I currently accessing a database using multiple queries and storing the results from the queries into DatatTables. I decided since I'm using multiple DataTables to store them inside a DataSet.
I can see that data is inside the DataTables when I print them out. However when I try to access them from the DataSet to print out the data, I get nothing back; it is empty.
string querytest1 = "SELECT * FROM test1";
string querytest2 = "SELECT * FROM test2";
string querytest3 = "SELECT * FROM test3";
using(OleDbConnection connection = new OleDbConnection(connectionString)){
OleDbCommand commandtest1 = new OleDbCommand(querytest1 , connection);
OleDbCommand commandtest2 = new OleDbCommand(querytest2 , connection);
OleDbCommand commandtest3 = new OleDbCommand(querytest3 , connection);
connection.Open();
DataSet dataSet = new DataSet();
OleDbDataAdapter dataAdaptertest1 = new OleDbDataAdapter(commandResults);
OleDbDataAdapter dataAdaptertest2 = new OleDbDataAdapter(commandResults);
OleDbDataAdapter dataAdaptertest3 = new OleDbDataAdapter(commandProjects);
DataTable dataTabletest1 = new DataTable();
DataTable dataTabletest2 = new DataTable();
DataTable dataTabletest3 = new DataTable();
dataAdaptertest1.Fill(dataTabletest1 );
dataAdaptertest2.Fill(dataTabletest2 );
dataAdaptertest3.Fill(dataTabletest3 );
dataTabletest1 = dataSet.Tables.Add("test1 ");
dataTabletest2 = dataSet.Tables.Add("test2 ");
dataTabletest3 = dataSet.Tables.Add("test3 ");
Console.WriteLine("DataSet has {0} DataTables \n", dataSet.Tables.Count);
foreach (DataTable objDt in dataSet.Tables)
Console.WriteLine("{0}", objDt.TableName);
return dataSet;
Expected behaviour: is to be able to access a DataTable from the DataSet and print out the data.
Example: Print out the contents in Test1
The code is redundant. I just don't know a better way to do this.

You don't need three adapters to fill a DataSet with the results from three commands.
You can simply write:
string query1 = "SELECT * FROM test1";
string query2 = "SELECT * FROM test2";
string query3 = "SELECT * FROM test3";
DataSet dataSet = new DataSet();
using(OleDbConnection connection = new OleDbConnection(connectionString)){
connection.Open();
OleDbCommand cmd = new OleDbCommand(q1, connection);
OleDbDataAdapter da = new OleDbDataAdapter(cmd);
da.Fill(ds, "Test1");
cmd.CommandText = q2;
da = new OleDbDataAdapter(cmd);
da.Fill(ds, "Test2");
cmd.CommandText = q3;
da = new OleDbDataAdapter(cmd);
da.Fill(ds, "Test3");
}
Console.WriteLine("DataSet has {0} DataTables \n", ds.Tables.Count);
foreach (DataTable objDt in ds.Tables)
Console.WriteLine("{0}", objDt.TableName);
The trick is filling the same DataSet three times instead of three different DataTables and giving at each fill a different name for each table created.

But, don't you see that dataSet.Tables.Add() call actually creates new DataTable instance, and trying to set its TableName property to "test1 " (btw. take care, space is not allowed in TableName).
That newly created instance(s) are set to properties dataTabletest1...3 - so, you lose access to the original ones, initially populated with data from the database.
You should do something like this:
DataTable dataTabletest1 = dataSet.Tables.Add("Test1");
DataTable dataTabletest2 = dataSet.Tables.Add("Test2");
DataTable dataTabletest3 = dataSet.Tables.Add("Test3");
dataAdaptertest1.Fill(dataTabletest1);
dataAdaptertest2.Fill(dataTabletest2);
dataAdaptertest3.Fill(dataTabletest3);
Please, check: https://learn.microsoft.com/en-us/dotnet/framework/data/adonet/dataset-datatable-dataview/adding-a-datatable-to-a-dataset

how fill gridview in foreach

How can I fill a GridView in foreach because this code bring last row just not all.
foreach (int i in userdetails)
{
SqlConnection con = new SqlConnection("*****");
SqlCommand cmd = new SqlCommand("********=" + i, con);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
da.Fill(ds);
gvSelected.Visible = true;
gvSelected.DataSource = ds;
gvSelected.DataBind();
}

You will want to do something more like this. Only get the data in the loop.
Notice I also used a SqlParameter which is important to prevent SQL Injection and avoid syntax errors.
SqlConnection con = new SqlConnection("*****");
SqlCommand cmd = new SqlCommand("********=#id", con);
SqlParameter parId = new SqlParameter("#id", SqlDbType.Int);
cmd.Parameters.Add(parId);
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
foreach (int i in userdetails)
{
parId.Value = i;
da.Fill(ds);
}
gvSelected.Visible = true;
gvSelected.DataSource = ds;
gvSelected.DataBind();
Of course you should consider trying to send all ids at once if possible. You would need something like a Table Valued parameter for that.

Get Contents of Last Record in DataGridView using C#

I am creating an application in which I am getting some data in my dataGridView1 in my form. I want to access my last row of data in some variables like I want to store columns in variables and use them. I know how to do this in GridView Cell click event but I want to use this in a loop like after every 10 seconds new data comes from database to dataGridView1 and I want last row to be accessed in variables.
Below is the code of how I am loading data in dataGridView
using (var con = new SqlConnection(ConStr))
{
string query = "SELECT * FROM CHECKINOUT";
using (var cmd = new SqlCommand(query, con))
{
con.Open();
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
da.Fill(ds);
dataGridView1.DataSource = ds.Tables[0].DefaultView;
}
}

Can you not just access the last row of Table 0 in your dataset and then assign all columns to variables
int lastRow = 0;
lastRow = ds.Tables(0).rows.count - 1;
string col1 = ds.Tables(0).Rows(lastRow)(0).tostring.trim;
Using your code you could do:
using (var con = new SqlConnection(ConStr))
{
string query = "SELECT * FROM CHECKINOUT";
using (var cmd = new SqlCommand(query, con))
{
con.Open();
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
da.Fill(ds);
dataGridView1.DataSource = ds.Tables[0].DefaultView;
}
}
int lastRow = 0;
lastRow = ds.Tables(0).rows.count - 1;
string col1 = ds.Tables(0).Rows(lastRow)(0).tostring.trim;
string col2 = ds.Tables(0).Rows(lastRow)(1).tostring.trim;
string col3 = ds.Tables(0).Rows(lastRow)(2).tostring.trim;

C# how to prevent duplicated data in the database?

how am i going prevent "lesson Title" from duplicating in database when user input duplicate data?
SqlConnection cnn = new SqlConnection();
SqlCommand cmd = new SqlCommand();
SqlDataAdapter da = new SqlDataAdapter();
SqlCommandBuilder cb = new SqlCommandBuilder(da);
DataSet ds = new DataSet();
cnn.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["Project1ConnectionString"].ConnectionString;
cnn.Open();
cmd.CommandText = "select * from Lesson";
cmd.Connection = cnn;
da.SelectCommand = cmd;
da.Fill(ds, "Lesson");
DataRow drow = ds.Tables["Lesson"].NewRow();
drow["TopicID"] = DropDownList1.Text;
drow["LessonTitle"] = TextBox1.Text;
drow["LessonDate"] = DateTime.Now;
ds.Tables["Lesson"].Rows.Add(drow);
da.Update(ds, "Lesson");

That kind of uniqueness should be enforced by the database. Add a unique constraint to your table:
CREATE UNIQUE INDEX UK_Lesson_Title ON Lesson (Title)

You can create a function to check the duplicate LessonTitle.
Explanantion: here i have created a function called checkDuplicateTitle().
this function takes AllRows of a LessonTable as DataRowCollection and LessonTitle to be verified as inputs.
it will check the LessonTitle of each and every row.
if given LessonTitle is matched with existing Titles from Table then this function returns true else returns false.
if the returned value is true we will ignore the updating the table with new row as LessonTitle is already Existing otherwise we will add it.
Code as below:
void UpdateLessonTable()
{
SqlConnection cnn = new SqlConnection();
SqlCommand cmd = new SqlCommand();
SqlDataAdapter da = new SqlDataAdapter();
SqlCommandBuilder cb = new SqlCommandBuilder(da);
DataSet ds = new DataSet();
cnn.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings["Project1ConnectionString"].ConnectionString;
cnn.Open();
cmd.CommandText = "select * from Lesson";
cmd.Connection = cnn;
da.SelectCommand = cmd;
da.Fill(ds, "Lesson");
if (!checkDuplicateTitle(ds.Tables["Lesson"].Rows, textBox1.Text.ToString()))
{
DataRow drow = ds.Tables["Lesson"].NewRow();
drow["TopicID"] = DropDownList1.Text;
drow["LessonTitle"] = TextBox1.Text;
drow["LessonDate"] = DateTime.Now;
ds.Tables["Lesson"].Rows.Add(drow);
da.Update(ds, "Lesson");
}
else
{
//you can display some warning here
// MessageBox.Show("Duplicate Lesson Title!");
}
}
//function for checking duplicate LessonTitle
bool checkDuplicateTitle(DataRowCollection rowTitle,String newTitle)
{
foreach (DataRow row in rowTitle)
{
if(row["LessonTitle"].Equals(newTitle))
return true;
}
return false;
}

Loop through ado.net sql select to add more rows to datatable

I currently have a working query for the first element in the array of ID's as seen below. What I need to do is add a for loop so I rerun the query for every element in the array and add each new row to the datatable but I am not sure how I do this? Unless there is a way I can include all ID's of my array in the where clause so I retrieve all rows through first run.
PID[] is a string array and could have anywhere from 1 to 5 elements that are random ID's.
Any help would be appreciated!
for loop here?
string firstQuery = "select * from Property p " +
"where p.id in (#pID)";
connString.Open();
SqlCommand selectAll = new SqlCommand(firstQuery, connString);
selectAll.Parameters.AddWithValue("#pID", PID[0]);
SqlDataAdapter adapter = new SqlDataAdapter();
adapter.SelectCommand = selectAll;
DataSet ds = new DataSet();
adapter.Fill(ds);
connString.Close();
DataTable table = ds.Tables[0];

Yes you can include all ids in one parameter and get results that match them:
var parameters = new string[PID.Length];
var selectAll = new SqlCommand();
for (int i = 0; i < PID.Length; i++)
{
parameters[i] = string.Format("#Age{0}", i);
selectAll .Parameters.AddWithValue(parameters[i], PID[i]);
}
selectAll.CommandText = string.Format("SELECT * from Property p WHERE p.id IN ({0})", string.Join(", ", parameters));
selectAll.Connection = connString;
connString.Open();
SqlDataAdapter adapter = new SqlDataAdapter();
adapter.SelectCommand = selectAll;
DataSet ds = new DataSet();
adapter.Fill(ds);
connString.Close();
DataTable table = ds.Tables[0];