Okay basically I have a SQL Server database that has details in it.
Column names: Student_Id
, Student_name
, Unit_number
, Unit_grade
I would like to query this database using two textboxes where you enter the id
and unit_number
and it will return the results in a message box when a button is clicked.
Where the question marks in the code are is where I am unsure of how to display a message box with the result. Unless this is completely the wrong way of doing things, I am only starting out with SQL in C#
I shouldn't be prone to SQL Injection using parameters as far as I know?
try
{
string str = "SELECT * FROM Students WHERE (Student_Id, Unit_number LIKE '%' + @search + '%')";
SqlCommand command = new SqlCommand(str, connect);
command.Parameters.Add("@search", SqlDbType.NVarChar).Value = textBox1.Text;
command.Parameters.Add("@search", SqlDbType.NVarChar).Value = textBox2.Text;
connect.Open();
command.ExecuteNonQuery();
SqlDataAdapter dataAdapt = new SqlDataAdapter();
dataAdapt.SelectCommand = command;
DataSet dataSet = new DataSet();
dataAdapt.Fill(dataSet, "Student_Id, Unit_number");
//?
//?
connect.Close();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
Your SQL is wrong in that your WHERE clause is syntactically incorrect. You probably want something like:
string str = "SELECT * FROM Students WHERE Student_ID = @id AND " +
"Unit_number LIKE @search";
This assumes that Student_ID
is a text type. The syntax would be slightly different if it was a number.
You are trying to add the same parameter to the query twice, which you won't want. Instead you'd want two parameters to match with the new SQL definition:
command.Parameters.Add("id", SqlDbType.NVarChar).Value =
textBox1.Text;
command.Parameters.Add("search", SqlDbType.NVarChar).Value =
"%" + textBox2.Text + "%";
Running ExecuteNonQuery
on the SqlCommand object doesn't do much for you as it is a query and you're not asking for the result back.
If you're only expecting one table back from your query, you'd probably be better off with a DataTable
rather than a DataSet
(the DataSet can contain many tables which is overkill for what you need).
try
{
string str = "SELECT * FROM Students WHERE Student_Id = @id AND " +
"Unit_number LIKE @search";
connect.Open();
SqlCommand command = new SqlCommand(str, connect);
command.Parameters.Add("id", SqlDbType.NVarChar).Value =
textBox1.Text;
command.Parameters.Add("search", SqlDbType.NVarChar).Value =
"%" + textBox2.Text + "%";
SqlDataAdapter dataAdapt = new SqlDataAdapter();
dataAdapt.SelectCommand = command;
DataTable dataTable = new DataTable();
dataAdapt.Fill(dataTable);
// At this point you should have a DataTable with some results in it.
// This is not going to be the best way of displaying data,
// but it should show you _something_
// It just iterates through the rows showing the columns
// which you've shown as being in your data.
foreach (DataRow dr in dataTable.Rows)
{
MessageBox.Show(String.Format("{0} - {1} - {2} - {3}",
dr["Student_Id"], dr["Student_name"],
dr["Unit_number"], dr["Unit_grade"]));
}
connect.Close();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}
EDITED to change the parameter handling as it didn't quite do what was needed. The % symbols are not part of the parameter rather than the SQL string.
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