String or binary data would be truncated.

An exception of type 'System.InvalidOperationException' occurred in System.Data.dll but was not handled in user code
 
Additional information: The given value of type String from the data source cannot be converted to type nchar of the specified target column.
 
String or binary data would be truncated.

protected void Button1_Click(object sender, EventArgs e)
{
String strConnection = @"Data Source=MANOJ\SQLEXPRESS;Initial Catalog=MANOJ;Integrated Security=True";
 
string path = @"C:\Users\Manoj Kumar\Desktop\Update Folder\TESTING.xlsx";
//Create connection string to Excel work book
string excelConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + path + ";Extended Properties=\"Excel 12.0;HDR=Yes;IMEX=1\"";
//Create Connection to Excel work book
OleDbConnection excelConnection = new OleDbConnection(excelConnectionString);
OleDbCommand cmd = new OleDbCommand("select *from [Sheet1$]", excelConnection);
excelConnection.Open();
OleDbDataReader dReader;
dReader = cmd.ExecuteReader();
SqlBulkCopy sqlBulk = new SqlBulkCopy(strConnection);
//Give your Destination table name
sqlBulk.DestinationTableName = "TEST";
sqlBulk.WriteToServer(dReader); // Here i getting the above error
excelConnection.Close();
Response.Write("inserted");
}