Use char overload of string.Join, fix SparseFieldSetExpression

Author: bkoelman

src/JsonApiDotNetCore/Queries/Expressions/AnyExpression.cs

@@ -58,7 +58,7 @@ private string InnerToString(bool toFullString)
         builder.Append('(');
         builder.Append(toFullString ? TargetAttribute.ToFullString() : TargetAttribute);
         builder.Append(',');
-        builder.Append(string.Join(",", Constants.Select(constant => toFullString ? constant.ToFullString() : constant.ToString()).OrderBy(value => value)));
+        builder.Append(string.Join(',', Constants.Select(constant => toFullString ? constant.ToFullString() : constant.ToString()).OrderBy(value => value)));
         builder.Append(')');
 
         return builder.ToString();

src/JsonApiDotNetCore/Queries/Expressions/IncludeElementExpression.cs

@@ -62,7 +62,7 @@ private string InnerToString(bool toFullString)
         if (Children.Count > 0)
         {
             builder.Append('{');
-            builder.Append(string.Join(",", Children.Select(child => toFullString ? child.ToFullString() : child.ToString()).OrderBy(name => name)));
+            builder.Append(string.Join(',', Children.Select(child => toFullString ? child.ToFullString() : child.ToString()).OrderBy(name => name)));
             builder.Append('}');
         }
 

src/JsonApiDotNetCore/Queries/Expressions/IncludeExpression.cs

@@ -50,7 +50,7 @@ public override string ToFullString()
     private string InnerToString(bool toFullString)
     {
         IReadOnlyCollection<ResourceFieldChainExpression> chains = IncludeChainConverter.Instance.GetRelationshipChains(this);
-        return string.Join(",", chains.Select(field => toFullString ? field.ToFullString() : field.ToString()).Distinct().OrderBy(name => name));
+        return string.Join(',', chains.Select(field => toFullString ? field.ToFullString() : field.ToString()).Distinct().OrderBy(name => name));
     }
 
     public override bool Equals(object? obj)

src/JsonApiDotNetCore/Queries/Expressions/LogicalExpression.cs

@@ -78,7 +78,7 @@ private string InnerToString(bool toFullString)
 
         builder.Append(Operator.ToString().Camelize());
         builder.Append('(');
-        builder.Append(string.Join(",", Terms.Select(term => toFullString ? term.ToFullString() : term.ToString())));
+        builder.Append(string.Join(',', Terms.Select(term => toFullString ? term.ToFullString() : term.ToString())));
         builder.Append(')');
 
         return builder.ToString();

src/JsonApiDotNetCore/Queries/Expressions/MatchTextExpression.cs

@@ -71,8 +71,8 @@ private string InnerToString(bool toFullString)
         builder.Append('(');
 
         builder.Append(toFullString
-            ? string.Join(",", TargetAttribute.ToFullString(), TextValue.ToFullString())
-            : string.Join(",", TargetAttribute, TextValue));
+            ? string.Join(',', TargetAttribute.ToFullString(), TextValue.ToFullString())
+            : string.Join(',', TargetAttribute, TextValue));
 
         builder.Append(')');
 

src/JsonApiDotNetCore/Queries/Expressions/PaginationQueryStringValueExpression.cs

@@ -32,12 +32,12 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
 
     public override string ToString()
     {
-        return string.Join(",", Elements.Select(element => element.ToString()));
+        return string.Join(',', Elements.Select(element => element.ToString()));
     }
 
     public override string ToFullString()
     {
-        return string.Join(",", Elements.Select(element => element.ToFullString()));
+        return string.Join(',', Elements.Select(element => element.ToFullString()));
     }
 
     public override bool Equals(object? obj)

src/JsonApiDotNetCore/Queries/Expressions/ResourceFieldChainExpression.cs

@@ -45,12 +45,12 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
 
     public override string ToString()
     {
-        return string.Join(".", Fields.Select(field => field.PublicName));
+        return string.Join('.', Fields.Select(field => field.PublicName));
     }
 
     public override string ToFullString()
     {
-        return string.Join(".", Fields.Select(field => $"{field.Type.PublicName}:{field.PublicName}"));
+        return string.Join('.', Fields.Select(field => $"{field.Type.PublicName}:{field.PublicName}"));
     }
 
     public override bool Equals(object? obj)

src/JsonApiDotNetCore/Queries/Expressions/SortExpression.cs

@@ -43,12 +43,12 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
 
     public override string ToString()
     {
-        return string.Join(",", Elements.Select(child => child.ToString()));
+        return string.Join(',', Elements.Select(child => child.ToString()));
     }
 
     public override string ToFullString()
     {
-        return $"{string.Join(",", Elements.Select(child => child.ToFullString()))}{(IsAutoGenerated ? " (auto-generated)" : "")}";
+        return $"{string.Join(',', Elements.Select(child => child.ToFullString()))}{(IsAutoGenerated ? " (auto-generated)" : "")}";
     }
 
     public override bool Equals(object? obj)

src/JsonApiDotNetCore/Queries/Expressions/SparseFieldSetExpression.cs

@@ -33,12 +33,12 @@ public override TResult Accept<TArgument, TResult>(QueryExpressionVisitor<TArgum
 
     public override string ToString()
     {
-        return string.Join(",", Fields.Select(field => field.PublicName).OrderBy(name => name));
+        return string.Join(',', Fields.Select(field => field.PublicName).OrderBy(name => name));
     }
 
     public override string ToFullString()
     {
-        return string.Join(".", Fields.Select(field => $"{field.Type.PublicName}:{field.PublicName}").OrderBy(name => name));
+        return string.Join(',', Fields.Select(field => $"{field.Type.PublicName}:{field.PublicName}").OrderBy(name => name));
     }
 
     public override bool Equals(object? obj)