Change DataTable ColumnType after loading data

Giving Dataset as input

private DataSet ChangeDataTableColumnType(DataSet ds,string tablename,string columnName,Type dataType)
{
DataTable dt = ChangeDataTableColumnType(ds.Tables[tablename], columnName, dataType);
ds.Tables.Remove(tablename);
ds.Tables.Add(dt);
return ds;
}

Giving DataTable as input

private DataTable ChangeDataTableColumnType(DataTable dt,string columnName,Type dataType)
{
DataTable newDt = dt.Clone();
newDt.Columns[columnName].DataType = dataType;
newDt.Merge(dt, true, MissingSchemaAction.Ignore);
return newDt;
}