Minor cleanup

Author: ranma42

src/EFCore.SqlServer/Query/Internal/SqlServerSqlTranslatingExpressionVisitor.cs

@@ -241,14 +241,7 @@ protected override Expression VisitMethodCall(MethodCallExpression methodCallExp
 
                 // CONCAT_WS filters out nulls, but string.Join treats them as empty strings; so coalesce (which is a no-op for non-nullable
                 // arguments).
-                arguments[i + 1] = sqlArgument switch
-                {
-                    ColumnExpression { IsNullable: false } => sqlArgument,
-                    SqlConstantExpression constantExpression => constantExpression.Value is null
-                        ? _sqlExpressionFactory.Constant(string.Empty)
-                        : constantExpression,
-                    _ => Dependencies.SqlExpressionFactory.Coalesce(sqlArgument, _sqlExpressionFactory.Constant(string.Empty))
-                };
+                arguments[i + 1] = Dependencies.SqlExpressionFactory.Coalesce(sqlArgument, _sqlExpressionFactory.Constant(string.Empty));
             }
 
             // CONCAT_WS never returns null; a null delimiter is interpreted as an empty string, and null arguments are skipped

src/EFCore.SqlServer/Query/Internal/Translators/SqlServerStringAggregateMethodTranslator.cs

@@ -80,14 +80,10 @@ public SqlServerStringAggregateMethodTranslator(
             }
         }
 
-        // STRING_AGG filters out nulls, but string.Join treats them as empty strings; coalesce unless we know we're aggregating over
-        // a non-nullable column.
-        if (sqlExpression is not ColumnExpression { IsNullable: false })
-        {
-            sqlExpression = _sqlExpressionFactory.Coalesce(
-                sqlExpression,
-                _sqlExpressionFactory.Constant(string.Empty, typeof(string)));
-        }
+        // STRING_AGG filters out nulls, but string.Join treats them as empty strings.
+        sqlExpression = _sqlExpressionFactory.Coalesce(
+            sqlExpression,
+            _sqlExpressionFactory.Constant(string.Empty, typeof(string)));
 
         // STRING_AGG returns null when there are no rows (or non-null values), but string.Join returns an empty string.
         return

src/EFCore.Sqlite.Core/Query/Internal/Translators/SqliteStringAggregateMethodTranslator.cs

@@ -60,12 +60,9 @@ public SqliteStringAggregateMethodTranslator(ISqlExpressionFactory sqlExpression
             return null;
         }
 
-        if (sqlExpression is not ColumnExpression { IsNullable: false })
-        {
-            sqlExpression = _sqlExpressionFactory.Coalesce(
-                sqlExpression,
-                _sqlExpressionFactory.Constant(string.Empty, typeof(string)));
-        }
+        sqlExpression = _sqlExpressionFactory.Coalesce(
+            sqlExpression,
+            _sqlExpressionFactory.Constant(string.Empty, typeof(string)));
 
         if (source.Predicate != null)
         {