公司帐户在SharePoint上读取Excel文件时，访问被条件访问策略阻止-出现错误。

出现“公司帐户在SharePoint上读取Excel文件时，访问被条件访问策略阻止-出现错误。”的问题，可能是由于访问策略限制了公司帐户对Excel文件的访问权限。以下是一种解决方法，包含代码示例：

1. 检查访问策略设置：首先，确保访问策略没有限制公司帐户对Excel文件的访问权限。可以通过以下代码示例来检查和修改访问策略：

using Microsoft.SharePoint.Client;

string siteUrl = "https://your-sharepoint-site-url";
string libraryName = "Documents";
string fileName = "your-excel-file.xlsx";

ClientContext clientContext = new ClientContext(siteUrl);
List documentsList = clientContext.Web.Lists.GetByTitle(libraryName);
ListItem listItem = documentsList.GetItemById(1); // Replace 1 with the actual ID of the Excel file

clientContext.Load(listItem, item => item.EffectiveBasePermissions);
clientContext.ExecuteQuery();

// Check the permissions of the company account
if (listItem.EffectiveBasePermissions.Has(PermissionKind.OpenItems))
{
    // The company account has permission to access the Excel file
    Console.WriteLine("Company account has access to the Excel file.");
}
else
{
    // The company account does not have permission to access the Excel file
    Console.WriteLine("Company account does not have access to the Excel file.");
}

2. 更新访问策略：如果发现访问策略限制了公司帐户对Excel文件的访问权限，可以使用以下代码示例来更新访问策略，以允许公司帐户访问：

using Microsoft.SharePoint.Client;

string siteUrl = "https://your-sharepoint-site-url";
string libraryName = "Documents";
string fileName = "your-excel-file.xlsx";

ClientContext clientContext = new ClientContext(siteUrl);
List documentsList = clientContext.Web.Lists.GetByTitle(libraryName);
ListItem listItem = documentsList.GetItemById(1); // Replace 1 with the actual ID of the Excel file

listItem.BreakRoleInheritance(false, true); // Remove unique permissions

// Add permission for the company account
string companyAccountName = "your-company-account";
Principal companyAccount = clientContext.Web.EnsureUser(companyAccountName);
RoleDefinitionBindingCollection roleDefinitionBindingCollection = new RoleDefinitionBindingCollection(clientContext);
roleDefinitionBindingCollection.Add(clientContext.Web.RoleDefinitions.GetByType(RoleType.Reader)); // Replace with the appropriate role type
listItem.RoleAssignments.Add(companyAccount, roleDefinitionBindingCollection);

clientContext.ExecuteQuery();

Console.WriteLine("Access to the Excel file has been granted to the company account.");

请根据实际情况修改代码示例中的URL、文件库名称、文件名和公司帐户名称等参数。这些示例代码使用了SharePoint CSOM (Client-Side Object Model) 来操作SharePoint。