C#

/// <summary>
/// Load a sheet from an Excel file
/// </summary>
/// <param name="path">Path to excel file</param>
/// <param name="columns">Comma separated list of columns to load. If not specified, loads all</param>
/// <param name="sheet">Sheet name to load. If not specified, loads "Sheet1$"</param>
/// <param name="verify">If true, checks that the file and sheet exist, and throws exceptions if not. Defaults to true</param>
/// <returns>Table of data retrieved.</returns>
public static System.Data.DataTable LoadExcel(string path, string columns = "*", string sheet = "Sheet1$", bool verify = true)
    {
    if (verify)
        {
        if (!File.Exists(path)) throw new IOException("The input file does not exist: " + path);
        if (!GetExcelSheetNames(path).Contains(sheet)) throw new ArgumentException("The requested sheet does not exist: " + sheet);
        }
    if (string.IsNullOrWhiteSpace(columns)) columns = "*";

    System.Data.DataTable dt = new System.Data.DataTable();
    using (OleDbConnection con = new OleDbConnection(GetExcelConnectionString(path)))
        {
        con.Open();
        string cmdStr = string.Format("SELECT {0} FROM [{1}]", columns, sheet);
        using (OleDbCommand cmd = new OleDbCommand(cmdStr, con))
            {
            using (OleDbDataAdapter da = new OleDbDataAdapter(cmd))
                {
                da.Fill(dt);
                }
            }
        }
    return dt;
    }
/// <summary>
/// Returns a list of all sheet names in an Excel File.
/// </summary>
/// <param name="path"></param>
/// <returns></returns>
public static List<string> GetExcelSheetNames(string path)
    {
    List<string> sheetNames = new List<string>();
    using (OleDbConnection con = new OleDbConnection(GetExcelConnectionString(path)))
        {
        con.Open();
        using (DataTable sheets = con.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null))
            {
            foreach (DataRow sheet in sheets.Rows)
                {
                if (sheet["TABLE_NAME"].ToString().Contains("$"))
                    {
                    // Filtered to just sheets - they all end in '$'
                    sheetNames.Add(sheet["TABLE_NAME"].ToString());
                    }
                }
            }
        }
    return sheetNames;
    }
/// <summary>
/// Returns a connection string for an Excel file
/// </summary>
/// <param name="path"></param>
/// <returns></returns>
private static string GetExcelConnectionString(string path)
    {
    return string.Format(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0}; Extended Properties=Excel 12.0", path);
    }

/// <summary>
/// Load data into SQL from a DataTable
/// </summary>
/// <param name="strConnect"></param>
/// <param name="tableName"></param>
/// <param name="table"></param>
public static void LoadSql(string strConnect, string tableName, DataTable table)
    {
    using (SqlConnection con = new SqlConnection(strConnect))
        {
        try
            {
            con.Open();
            using (SqlBulkCopy bulk = new SqlBulkCopy(con))
                {
                bulk.DestinationTableName = tableName;
                bulk.WriteToServer(table);
                }
            }
        finally
            {
            con.Close();
            }
        }
    }

OriginalGriff wrote:

and being able to transfer the data from the one to the other makes life a lot easier

C# Language Specification[^]:

A foreach statement of the form

C#

foreach (V v in x) embedded-statement

is then expanded to:

C#

{
    E e = ((C)(x)).GetEnumerator();
    try {
        while (e.MoveNext()) {
            V v = (V)(T)e.Current;
            embedded-statement
        }
    }
    finally {
        // Dispose e
    }
}

Rob Philpott wrote:

I can do this is a 'streaming' approach which would be faster and not require as much memory.