added dependecy usings based on types present in renderContext

Author: sakets594

packages/quicktype-core/src/language/CSharp/CSharpRenderer.ts

@@ -10,7 +10,7 @@ import { assert } from "../../support/Support";
 import { type TargetLanguage } from "../../TargetLanguage";
 import { followTargetType } from "../../Transformers";
 import { type ClassProperty, type ClassType, type EnumType, type Type, type UnionType } from "../../Type";
-import { directlyReachableSingleNamedType, matchType, nullableFromUnion, removeNullFromUnion } from "../../TypeUtils";
+import { directlyReachableSingleNamedType, matchCompoundType, matchType, nullableFromUnion, removeNullFromUnion } from "../../TypeUtils";
 
 import { type cSharpOptions } from "./language";
 import {
@@ -387,4 +387,21 @@ export class CSharpRenderer extends ConvenienceRenderer {
 
         this.emitDefaultFollowingComments();
     }
+
+    protected emitDependencyUsings(): void {
+        let nameSpaceForTypes: string[] = [];
+        this.typeGraph.allTypesUnordered().forEach(_ => {
+            matchCompoundType(
+                _,
+                _arrayType => this._csOptions.useList ? nameSpaceForTypes.push("System.Collections.Generic") : undefined,
+                _classType => { },
+                _mapType => nameSpaceForTypes.push("System.Collections.Generic"),
+                _objectType => { },
+                _unionType => { }
+            )
+        });
+        nameSpaceForTypes = nameSpaceForTypes.filter((val, ind) => nameSpaceForTypes.indexOf(val) === ind );
+        nameSpaceForTypes.forEach(this.emitUsing.bind(this));
+    }
+
 }

packages/quicktype-core/src/language/CSharp/NewtonSoftCSharpRenderer.ts

@@ -120,8 +120,10 @@ export class NewtonsoftCSharpRenderer extends CSharpRenderer {
     }
 
     protected emitUsings(): void {
-        // FIXME: We need System.Collections.Generic whenever we have maps or use List.
-        if (!this._needAttributes && !this._needHelpers) return;
+        if (!this._needAttributes && !this._needHelpers) {
+            this.emitDependencyUsings();
+            return;
+        }
 
         super.emitUsings();
         this.ensureBlankLine();

packages/quicktype-core/src/language/CSharp/SystemTextJsonCSharpRenderer.ts

@@ -120,8 +120,10 @@ export class SystemTextJsonCSharpRenderer extends CSharpRenderer {
     }
 
     protected emitUsings(): void {
-        // FIXME: We need System.Collections.Generic whenever we have maps or use List.
-        if (!this._needAttributes && !this._needHelpers) return;
+        if (!this._needAttributes && !this._needHelpers) {
+            this.emitDependencyUsings();
+            return;
+        }
 
         super.emitUsings();
         this.ensureBlankLine();