Add project files.

src/modules/Elsa.Sql/Activities/SqlSingleValue.cs

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+using System.Runtime.CompilerServices;
+using Elsa.Expressions.Models;
+using Elsa.Extensions;
+using Elsa.Sql.Contracts;
+using Elsa.Sql.UIHints;
+using Elsa.Workflows;
+using Elsa.Workflows.Attributes;
+using Elsa.Workflows.Models;
+using Elsa.Workflows.UIHints;
+
+namespace Elsa.Sql.Activities;
+
+/// <summary>
+/// Execute given SQL command and return a single result.
+/// </summary>
+[Activity("Elsa", "SQL", "Execute given SQL command and return a single result.", DisplayName = "SQL Single Value", Kind = ActivityKind.Task)]
+public class SqlSingleValue : Activity
+{
+    /// <summary>
+    /// <inheritdoc/>
+    /// </summary>
+    public SqlSingleValue([CallerFilePath] string? source = null, [CallerLineNumber] int? line = null) : base(source, line)
+    {
+    }
+
+    /// <summary>
+    /// Database client to connect with.
+    /// </summary>
+    [Input(
+        Description = "Database client.",
+        UIHint = InputUIHints.DropDown,
+        UIHandler = typeof(SqlClientsDropDownProvider))]
+    public Input<string?> Client { get; set; } = null!;
+
+    /// <summary>
+    /// Connection string.
+    /// </summary>
+    [Input(
+        Description = "Connection string.",
+        CanContainSecrets = true)]
+    public Input<string?> ConnectionString { get; set; } = null!;
+
+    /// <summary>
+    /// Command to run against the database.
+    /// </summary>
+    [Input(
+        Description = "Query to run against the database.",
+        DefaultSyntax = "Sql",
+        UIHint = InputUIHints.CodeEditor,
+        UIHandler = typeof(SqlCodeOptionsProvider)
+    )]
+    public Input<string?> Command { get; set; } = null!;
+
+
+    /// <summary>
+    /// Command result.
+    /// </summary>
+    [Output(
+        Description = "Command result.")]
+    public Output<object?> Result { get; set; } = null!;
+
+
+    /// <summary>
+    /// <inheritdoc/>
+    /// </summary>
+    protected override async ValueTask ExecuteAsync(ActivityExecutionContext context)
+    {
+        var command = Command.GetOrDefault(context);
+
+        // If no command was specified, there's nothing to do.
+        if (string.IsNullOrWhiteSpace(command))
+            return;
+
+        // Get and execute the SQL evaluator.
+        var evaluator = context.GetRequiredService<ISqlEvaluator>();
+        var evaluatedQuery = await evaluator.EvaluateAsync(command, context.ExpressionExecutionContext, new ExpressionEvaluatorOptions(), context.CancellationToken);
+
+        // Create client
+        var factory = context.GetRequiredService<ISqlClientFactory>();
+        var client = factory.CreateClient(Client.GetOrDefault(context), ConnectionString.GetOrDefault(context));
+
+        // Execute command
+        var result = await client.ExecuteScalarAsync(evaluatedQuery);
+        context.Set(Result, result);
+
+        await CompleteAsync(context);
+    }
+}