How to change executescalar(); for more select resultsin one string

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I have a method which returns value from database to a string. Now i have a problem because there is more than one result of the SELECT and I need to change ExecuteScalar(); to something else. I want to have these SELECT results in one string.

What I have tried:

string GetModule (string aplS) 
            {
                SqlConnection maConn = new SqlConnection("Data Source=xxx;Initial 
                Catalog=xx;User ID=xx;Password=xxx");
                string query = "select distinct mod from MOD_slow where 
                 aplS='"+aplS+"'";
                System.Data.SqlClient.SqlCommand cmd = new 
                System.Data.SqlClient.SqlCommand(query, maConn);
                System.Data.DataTable dt = new System.Data.DataTable();
                macierzConn.Open();                
                var SavedString = (string)cmd.ExecuteScalar();
                SavedString= SavedString.TrimEnd();
                macierzConn.Close();
                return SavedString;                            

            }

Posted 26-May-20 2:38am

aksimoN

Updated 26-May-20 5:44am

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Maciej Los 26-May-20 8:45am

Can you be more specific and provide more details?

2 solutions

Solution 1

Either use ExecuteReader:

C#

using (SqlConnection con = new SqlConnection(strConnect))
    {
    con.Open();
    using (SqlCommand cmd = new SqlCommand("SELECT Age, Description FROM myTable WHERE ID = @ID", con))
        {
        cmd.Parameters.AddWithValue("@ID", myTextBox.Text);
        using (SqlDataReader reader = cmd.ExecuteReader())
            {
            while (reader.Read())
                {
                int age = (int) reader["Age"];
                string desc = (string) reader["Description"];
                Console.WriteLine($"{age}\n{desc}");
                }
            }
        }
    }

Or a SqlDataAdapter:

C#

using (SqlConnection con = new SqlConnection(strConnect))
    {
    con.Open();
    using (SqlDataAdapter da = new SqlDataAdapter("SELECT Age, Description FROM myTable WHERE ID = @ID", con))
        {
        da.SelectCommand.Parameters.AddWithValue("@ID", myTextBox.Text);
        DataTable dt = new DataTable();
        da.Fill(dt);
        myDataGridView.DataSource = dt;
        }
    }

Posted 26-May-20 2:48am

OriginalGriff

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Garth J Lancaster · Accepted Answer · 2020-05-26T03:07:00

Well, 1st up, look at that HORRIBLE, DANGEROUS SQL - please dont do this - please use paramterized SQL

SqlCommand cmd = new SqlCommand(
    "select field from table where value = @Value", conn);

    SqlParameter param  = new SqlParameter();
    param.ParameterName = "@Value";
    param.Value         = *********;  // your actual value here 

    cmd.Parameters.Add(param);
    reader = cmd.ExecuteReader();

    while(reader.Read())
    {
        // Do something with the query result here 
        string colValue = reader["Column/Field Name"].ToString();
    }

2nd, you should use a 'using block' where possible, and forget the manual

macierzConn.Close();

so :-

using SqlConnection maConn = new SqlConnection("Data Source=xxx;Initial Catalog=xx;User ID=xx;Password=xxx")
{
    using SqlCommand cmd = new SqlCommand(
        "select field from table where value = @Value", conn);
    {
        SqlParameter param  = new SqlParameter();
        param.ParameterName = "@Value";
        param.Value         = *********;  // your actual value here 

        cmd.Parameters.Add(param);
    
        using SqlDataReader reader = cmd.ExecuteReader() 
        {
            while(reader.Read())
            {
                // Do something with the query result here 
                string colValue = reader["Column/Field Name"].ToString();
            }
        } // Using SqlDataReader 
    } // Using SqlCommand 
} // SqlConnection

That's pretty rough and needs tidying up, but its the 'more correct' way

You havnt actually said what you mean by

Quote:
results in one string.

maybe you use a StringBuilder and add to the string in the while(reader.Read() loop