.Net: Fix FunctionChoiceBehavior State Restoration in OllamaPromptExe…

…cutionSettings. (#9718)

### Description

This PR addresses a bug in `OllamaPromptExecutionSettings` where the
`FunctionChoiceBehavior` state was not properly restored during the
conversion process from `PromptExecutionSettings`. Specifically, the
internal state of `FunctionChoiceBehavior`, including its list of
associated functions, was lost during serialization and deserialization.

### Motivation and Context

**Why is this change required?**
The lack of proper state restoration led to missing function definitions
in HTTP requests when using the Ollama connector, causing failures in
scenarios that rely on function calls.

**What problem does it solve?**
This change ensures that the `FunctionChoiceBehavior` is fully restored
when converting execution settings, maintaining the expected behavior
for function calls in the Ollama connector.

**What scenario does it contribute to?**
This fix enables consistent and reliable function calling with the
Ollama connector, ensuring that defined functions are included in
requests and operate as expected.

**Related Issues**
This change fixes the issue described in the bug report, improving
usability and reliability when working with function behaviors in
Semantic Kernel integrations.

### Contribution Checklist

- [Y] The code builds clean without any errors or warnings
- [Y] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [Y] All unit tests pass, and I have added new tests where possible
- [Y] I didn't break anyone :)

Fixes #9682

---------

Co-authored-by: Adit Sheth <adsheth@microsoft.com>
Co-authored-by: Mark Wallace <127216156+markwallace-microsoft@users.noreply.github.com>

dotnet/src/Connectors/Connectors.Ollama.UnitTests/Settings/OllamaPromptExecutionSettingsTests.cs

@@ -62,4 +62,20 @@ public void FromExecutionSettingsWhenSerializedHasPropertiesShouldPopulateSpecia
         Assert.Equal(0.9f, ollamaExecutionSettings.TopP!.Value, 0.1f);
         Assert.Equal(100, ollamaExecutionSettings.TopK);
     }
+
+    [Fact]
+    public void FromExecutionSettingsShouldRestoreFunctionChoiceBehavior()
+    {
+        // Arrange
+        var functionChoiceBehavior = FunctionChoiceBehavior.Auto();
+
+        var originalExecutionSettings = new PromptExecutionSettings();
+        originalExecutionSettings.FunctionChoiceBehavior = functionChoiceBehavior;
+
+        // Act
+        var result = OllamaPromptExecutionSettings.FromExecutionSettings(originalExecutionSettings);
+
+        // Assert
+        Assert.Equal(functionChoiceBehavior, result.FunctionChoiceBehavior);
+    }
 }

dotnet/src/Connectors/Connectors.Ollama/Settings/OllamaPromptExecutionSettings.cs

@@ -30,14 +30,17 @@ public static OllamaPromptExecutionSettings FromExecutionSettings(PromptExecutio
 
         var json = JsonSerializer.Serialize(executionSettings);
         var ollamaExecutionSettings = JsonSerializer.Deserialize<OllamaPromptExecutionSettings>(json, JsonOptionsCache.ReadPermissive);
-        if (ollamaExecutionSettings is not null)
+        if (ollamaExecutionSettings is null)
         {
-            return ollamaExecutionSettings;
-        }
-
-        throw new ArgumentException(
+            throw new ArgumentException(
             $"Invalid execution settings, cannot convert to {nameof(OllamaPromptExecutionSettings)}",
             nameof(executionSettings));
+        }
+
+        // Restore the function choice behavior that lost internal state(list of function instances) during serialization/deserialization process.
+        ollamaExecutionSettings!.FunctionChoiceBehavior = executionSettings.FunctionChoiceBehavior;
+
+        return ollamaExecutionSettings;
     }
 
     /// <summary>