Промежуточное.

VisualComponentsLib/UserDataGridView.Designer.cs

@@ -28,10 +28,58 @@
         /// </summary>
         private void InitializeComponent()
         {
-            components = new System.ComponentModel.Container();
+            dataGridView = new DataGridView();
-            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
+            buttonAdd = new Button();
+            buttonClear = new Button();
+            ((System.ComponentModel.ISupportInitialize)dataGridView).BeginInit();
+            SuspendLayout();
+            // 
+            // dataGridView
+            // 
+            dataGridView.ColumnHeadersHeightSizeMode = DataGridViewColumnHeadersHeightSizeMode.AutoSize;
+            dataGridView.Location = new Point(3, 3);
+            dataGridView.Name = "dataGridView";
+            dataGridView.RowTemplate.Height = 25;
+            dataGridView.Size = new Size(417, 459);
+            dataGridView.TabIndex = 0;
+            // 
+            // buttonAdd
+            // 
+            buttonAdd.Location = new Point(446, 23);
+            buttonAdd.Name = "buttonAdd";
+            buttonAdd.Size = new Size(123, 23);
+            buttonAdd.TabIndex = 1;
+            buttonAdd.Text = "Добавить значение";
+            buttonAdd.UseVisualStyleBackColor = true;
+            buttonAdd.Click += ButtonAdd_Click;
+            // 
+            // buttonClear
+            // 
+            buttonClear.Location = new Point(446, 76);
+            buttonClear.Name = "buttonClear";
+            buttonClear.Size = new Size(123, 23);
+            buttonClear.TabIndex = 2;
+            buttonClear.Text = "Очистить всё";
+            buttonClear.UseVisualStyleBackColor = true;
+            buttonClear.Click += ButtonClear_Click;
+            // 
+            // UserDataGridView
+            // 
+            AutoScaleDimensions = new SizeF(7F, 15F);
+            AutoScaleMode = AutoScaleMode.Font;
+            Controls.Add(buttonClear);
+            Controls.Add(buttonAdd);
+            Controls.Add(dataGridView);
+            Name = "UserDataGridView";
+            Size = new Size(598, 465);
+            ((System.ComponentModel.ISupportInitialize)dataGridView).EndInit();
+            ResumeLayout(false);
         }
 
         #endregion
+
+        private DataGridView dataGridView;
+        private Button buttonAdd;
+        private Button buttonClear;
     }
 }

VisualComponentsLib/UserDataGridView.cs

@@ -12,9 +12,22 @@ namespace VisualComponentsLib
 {
     public partial class UserDataGridView : UserControl
     {
+
+
         public UserDataGridView()
         {
             InitializeComponent();
         }
+
+        private void ButtonAdd_Click(object sender, EventArgs e)
+        {
+
+        }
+
+        //полная очистка
+        private void ButtonClear_Click(object sender, EventArgs e)
+        {
+            dataGridView.Rows.Clear();
+        }
     }
 }

VisualComponentsLib/UserDataGridView.resx

@@ -18,7 +18,7 @@
     <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
     <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
     <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
-    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing"">Blue</data>
     <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
         <value>[base64 mime encoded serialized .NET Framework object]</value>
     </data>

VisualComponentsLib/UserTextBox.Designer.cs

@@ -28,10 +28,42 @@
         /// </summary>
         private void InitializeComponent()
         {
-            components = new System.ComponentModel.Container();
+            checkBox = new CheckBox();
-            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
+            textBox = new TextBox();
+            SuspendLayout();
+            // 
+            // checkBox
+            // 
+            checkBox.AutoSize = true;
+            checkBox.Location = new Point(14, 52);
+            checkBox.Name = "checkBox";
+            checkBox.Size = new Size(104, 19);
+            checkBox.TabIndex = 0;
+            checkBox.Text = "Включить null";
+            checkBox.UseVisualStyleBackColor = true;
+            // 
+            // textBox
+            // 
+            textBox.Location = new Point(14, 12);
+            textBox.Name = "textBox";
+            textBox.Size = new Size(182, 23);
+            textBox.TabIndex = 2;
+            // 
+            // UserTextBox
+            // 
+            AutoScaleDimensions = new SizeF(7F, 15F);
+            AutoScaleMode = AutoScaleMode.Font;
+            Controls.Add(textBox);
+            Controls.Add(checkBox);
+            Name = "UserTextBox";
+            Size = new Size(210, 80);
+            ResumeLayout(false);
+            PerformLayout();
         }
 
         #endregion
+
+        private CheckBox checkBox;
+        private TextBox textBox;
     }
 }

VisualComponentsLib/UserTextBox.cs

@@ -12,9 +12,50 @@ namespace VisualComponentsLib
 {
     public partial class UserTextBox : UserControl
     {
+        public string inputString
+        {
+            get => textBox.Text;
+            set => textBox.Text = value;
+        }
+
+        public new event EventHandler? TextChanged
+        {
+            add => textBox.Text = value.ToString();
+            remove => textBox.Text = string.Empty;
+        }
+
         public UserTextBox()
         {
             InitializeComponent();
         }
+
+        public void clickCheckBox()
+        {
+            if(checkBox.Checked)
+            {
+                textBox.ReadOnly = true;
+
+                inputString = string.Empty;
+
+                textBox.Text = string.Empty;
+            }
+            
+            if(!checkBox.Checked)
+            {
+                try
+                {
+                    double support;
+
+                    if (Double.TryParse(textBox.Text, out support))
+                    {
+                        inputString = textBox.Text;
+                    }
+                }
+                catch (Exception ex)
+                {
+                    MessageBox.Show("Введённое значение не является вещественным числом.");
+                }
+            }
+        }
     }
 }

VisualComponentsLib/UserTextBox.resx

@@ -18,7 +18,7 @@
     <resheader name="reader">System.Resources.ResXResourceReader, System.Windows.Forms, ...</resheader>
     <resheader name="writer">System.Resources.ResXResourceWriter, System.Windows.Forms, ...</resheader>
     <data name="Name1"><value>this is my long string</value><comment>this is a comment</comment></data>
-    <data name="Color1" type="System.Drawing.Color, System.Drawing">Blue</data>
+    <data name="Color1" type="System.Drawing.Color, System.Drawing"">Blue</data>
     <data name="Bitmap1" mimetype="application/x-microsoft.net.object.binary.base64">
         <value>[base64 mime encoded serialized .NET Framework object]</value>
     </data>