Add named WithVariable overload (#7701)

src/modules/Elsa.Workflows.Core/Builders/WorkflowBuilder.cs

@@ -88,6 +88,14 @@ public class WorkflowBuilder(IActivityVisitor activityVisitor, IIdentityGraphSer
         return variable;
     }
 
+    /// <inheritdoc />
+    public Variable<T> WithVariable<T>(string name)
+    {
+        var variable = new Variable<T>(name, default!);
+        Variables.Add(variable);
+        return variable;
+    }
+
     /// <inheritdoc />
     public Variable<T> WithVariable<T>(string name, T value)
     {
@@ -298,4 +306,4 @@ public class WorkflowBuilder(IActivityVisitor activityVisitor, IIdentityGraphSer
         await workflowDefinition.BuildAsync(this, cancellationToken);
         return await BuildWorkflowAsync(cancellationToken);
     }
-}
+}

src/modules/Elsa.Workflows.Core/Contracts/IWorkflowBuilder.cs

@@ -115,6 +115,11 @@ public interface IWorkflowBuilder
     [Obsolete("Use the overload that takes a name instead. This overload will be removed in a future version.")]
     Variable<T> WithVariable<T>();
     
+    /// <summary>
+    /// A fluent method for adding a variable to <see cref="Variables"/>.
+    /// </summary>
+    Variable<T> WithVariable<T>(string name);
+    
     /// <summary>
     /// A fluent method for adding a variable to <see cref="Variables"/>.
     /// </summary>
@@ -220,4 +225,4 @@ public interface IWorkflowBuilder
     /// Creates a new <see cref="Workflow"/> instance using the specified <see cref="IWorkflow"/> definition.
     /// </summary>
     Task<Workflow> BuildWorkflowAsync(IWorkflow workflowDefinition, CancellationToken cancellationToken = default);
-}
+}

test/integration/Elsa.Workflows.IntegrationTests/Serialization/VariableExpressions/Workflows.cs

@@ -7,7 +7,7 @@ class SampleWorkflow : WorkflowBase
 {
     protected override void Build(IWorkflowBuilder workflow)
     {
-        var variable1 = workflow.WithVariable("Some variable");
+        var variable1 = workflow.WithVariable<string>("Some variable");
         var variable2 = workflow.WithVariable(42);
         var literal1 = new Literal<string>("Some literal");
         var literal2 = new Literal<int>(84);
@@ -27,4 +27,4 @@ class SampleWorkflow : WorkflowBase
             }
         };
     }
-}   
+}