Azure Functions
An Azure service that provides an event-driven serverless compute platform.
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How to fix the error - Could not load file or assembly 'System.Memory.Data, Version, under the Azure Durable function
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(281.6, 81%, 37%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ERV%3C/text%3E%3C/svg%3E)
raviteja vemulakonda
0
Reputation points
I'm building a Azure Durable function with Python framework in my local VS Code. While I'm running the function in the visual studio, I'm getting the below error.
The listener for function 'Functions.orchestrator' was unable to start. Azure.Core: Could not load file or assembly 'System.Memory.Data, Version=6.0.0.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51'. The system cannot find the file specified.
I'm using the Azurite for the local storage and the services are also listening under the below ports.
Hi All,
Please find the below host.json and localsettings.json
host.json
{
"version": "2.0",
"extensionBundle": {
"id": "Microsoft.Azure.Functions.ExtensionBundle",
"version": "[4.*, 5.0.0)"
``` }
}
local settings.json
{
"IsEncrypted": false,
"Values": {
```yaml
"AzureWebJobsStorage": "DefaultEndpointsProtocol=http;AccountName=devstoreaccount1;AccountKey=Eby8vdM02xNOcqFlqUwJPLlmEtlCDXJ1OUzFT50uSRZ6IFsuFq2UVErCz4I6tq/K1SZFPTOtr/KBHBeksoGMGw==;BlobEndpoint=http://127.0.0.1:10000/devstoreaccount1;QueueEndpoint=http://127.0.0.1:10001/devstoreaccount1;TableEndpoint=http://127.0.0.1:10002/devstoreaccount1;",
"FUNCTIONS_WORKER_RUNTIME": "python",
"DurableFunctionsHubName": "MyDurableFunctionsHub"
``` }
}
Could some one help me in resolving the above error.
Azure Functions
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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(265.6, 22%, 35%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ESE%3C/text%3E%3C/svg%3E)
Shireesha Eeraboina 3,435 Reputation points Microsoft External Staff Moderator2025-06-23T17:02:37.37+00:00 Thanks for your query.
The error "Could not load file or assembly 'System.Memory.Data'" happens because the Azure Functions runtime is missing a required dependency.
Please try these steps to fix it:
- Update Azure Functions Core Tools Use version 4.x → Install Guide
- Update
host.jsonExtension Bundle
"extensionBundle": { "id": "Microsoft.Azure.Functions.ExtensionBundle", "version": "[4.11.0, 5.0.0)" }- Use Python 3.8, 3.9, or 3.10 only Supported Python Versions
- Install .NET 6 SDK Required by the runtime → Download .NET 6
- Upgrade Durable Functions Package
pip install --upgrade azure-functions-durableAfter that, restart VS Code and run:
func host startLet me know if the issue continues — happy to help further!
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Shireesha Eeraboina 3,435 Reputation points Microsoft External Staff Moderator
2025-06-24T14:01:54.24+00:00 I hope you had a chance to review the response above. If there are any updates or if you need further assistance, please feel free to update here.
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raviteja vemulakonda 0 Reputation points
2025-06-25T12:16:56.37+00:00 Hi @Shireesha Eeraboina ,
I have made the changes, but still getting the same error.
Please find the below configurations, that I'm using for building the durable function.
VS Code - 1.100.0
Python - 3.9
Core Tools Version - 4.0.5148
Function Runtime Version - 4.17.3.20392
.NET runtime - Microsoft.NETCore.App 6.0.16
Local Storage - Azurite
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Shireesha Eeraboina 3,435 Reputation points Microsoft External Staff Moderator
2025-06-26T14:32:09.9166667+00:00 If you are still facing the issue, could you please check the private message and provide the required details for further troubleshooting?
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