how to insert excel file into datata

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C#

MS-Excel

I have written the following code to insert data from multiple excel files sheet wise. But I get this error " '' is not a valid name. Make sure that it does not include invalid characters or punctuation and that it is not too long." Please help.

DataTable xls = new DataTable();
OleDbConnection SQLConn = new OleDbConnection(strConnectionString);

SQLConn.Open();

OleDbDataAdapter SQLAdapter = new OleDbDataAdapter();
string sql = "SELECT * FROM [" + sheetName + "]";
OleDbCommand selectCMD = new OleDbCommand(sql, SQLConn);

SQLAdapter.SelectCommand = selectCMD;

SQLAdapter.Fill(xls);

SQLConn.Close();