private void ImportFromExcel() { ImportTool frm = new ImportTool(); DialogResult result = frm.ShowDialog(); { var imports = frm.GetImports; StringBuilder builder = new StringBuilder(); string prevContent = richTextBoxLibraryContent.Text; builder.AppendLine(prevContent); foreach (var key in imports.Keys) { builder.AppendLine(key + "\t" + imports[key].ToString()); } richTextBoxLibraryContent.Text = builder.ToString(); } }