How do I add multiple rows in a table?

Question

string date = p_text_data.Text;
string sql = @"INSERT INTO Warehouse (title,count,price,date) ";
try
{
    using (SqlConnection connection = ConnectToDataBase.GetConnection())
    {
        SqlCommand command = new SqlCommand(sql, connection);
        for (int i = 0; i < mdc.Count; i++)
        {
            sql += "SELECT @title" + i + ",@count" + i + ",@price" + i + ",@date" + i + " ";
            command.Parameters.AddWithValue("@title" + i, mdc[i].Title);
            command.Parameters.AddWithValue("@count" + i, mdc[i].Count);
            command.Parameters.AddWithValue("@price" + i, mdc[i].Price);
            command.Parameters.AddWithValue("@date" + i, Conver_Data(date));
            if (mdc.Count-1 != i)
                sql += "UNION ALL ";
        }
        sql += " ;";
        connection.Open();// *sql
        string id_Partner = command.ExecuteScalar().ToString();
    }
}
catch (SqlException se)
{
    MessageBox.Show(se.Message);
}

*sql = "INSERT INTO Warehouse (title,count,price,date) SELECT @title0,@count0,@price0,@date0 UNION ALL SELECT @title1,@count1,@price1,@date1 ;"

Then he flies an exception

Incorrect syntax near ')'

clarify - count - int, price - double, date - Date

what am I doing wrong?

edit: Table

CREATE TABLE [dbo].[Warehouse] (
  [ID] int IDENTITY(1, 1) NOT NULL,
  [title] char(30) COLLATE Cyrillic_General_CI_AS NULL,
  [count] int NULL,
  [price] float NULL,
  [date] datetime NULL,
  CONSTRAINT [PK__Warehous__3214EC277F60ED59] PRIMARY KEY CLUSTERED ([ID])
)
ON [PRIMARY]
GO

I'm used SQL Server 2008

Answer 1

The problem is that you are never updating the SQL command text of the command object with anything after the ")". Just because you update the sql variable doesn't mean that SqlCommand object is going to see that update.

(Another problem that you will run into is that you are not returning anything from this query, so you won't be able to use ExecuteScalar().)

Try this instead:

string date = p_text_data.Text; 
string sql = @"INSERT INTO Warehouse (title,count,price,date) "; 
try 
{ 
    using (SqlConnection connection = ConnectToDataBase.GetConnection()) 
    { 
        SqlCommand command = new SqlCommand(sql, connection); 
        for (int i = 0; i < mdc.Count; i++) 
        { 
            sql += "SELECT @title" + i + ",@count" + i + ",@price" + i + ",@date" + i + " "; 
            command.Parameters.AddWithValue("@title" + i, mdc[i].Title); 
            command.Parameters.AddWithValue("@count" + i, mdc[i].Count); 
            command.Parameters.AddWithValue("@price" + i, mdc[i].Price); 
            command.Parameters.AddWithValue("@date" + i, Conver_Data(date)); 
            if (mdc.Count-1 != i) 
                sql += "UNION ALL "; 
        } 
        sql += " ;"; 
        command.CommandText = sql;    //  Set your SQL Command to the whole statement.
        connection.Open();// *sql 
        command.ExecuteNonQuery();    //  Execute a query with no return value.
    } 
} 
catch (SqlException se) 
{ 
    MessageBox.Show(se.Message); 
} 

Answer 2

You are trying to use the String sql as a reference type, although it is a reference type, it is a special case where it acts like a value type. The line

sql += "SELECT @title" + i + ",@count" + i + ",@price" + i + ",@date" + i + " ";

appears to be appending to sql but in fact it is creating a new string, stored in a different location in memory to String that you passed to the SqlCommand.

If you array is large you may see a performance benefit by using the StringBuilder class to build your string then assign it to your SqlCommand object after it has been built.

Either way you need to assign it to SqlCommand.CommandText after you have the complete SQL in your sql variable.