增加textbox默认文本

STS/Form2.Designer.cs

@@ -57,10 +57,16 @@
             // 
             // barcode_tb
             // 
+                this.barcode_tb.ForeColor = System.Drawing.SystemColors.GrayText;
             this.barcode_tb.Location = new System.Drawing.Point(124, 46);
             this.barcode_tb.Name = "barcode_tb";
             this.barcode_tb.Size = new System.Drawing.Size(234, 25);
             this.barcode_tb.TabIndex = 0;
+            this.barcode_tb.Text = "T*****";
+            this.barcode_tb.Click += new System.EventHandler(this.barcode_tb_Click);
+            this.barcode_tb.HideSelectionChanged += new System.EventHandler(this.barcode_tb_HideSelectionChanged);
+            this.barcode_tb.TextChanged += new System.EventHandler(this.barcode_tb_TextChanged);
+            this.barcode_tb.MouseLeave += new System.EventHandler(this.barcode_tb_MouseLeave);
             // 
             // STI_tb
             // 

STS/Form2.cs

@@ -61,9 +61,19 @@ namespace STS
             conn2.Open();
             SqlCommand cmd = new SqlCommand();
             cmd.Connection = conn2;
+            //判断数据库中是否已经有该条码
+            cmd.CommandText = $"select * from STM where Barcode='{barcode_tb.Text}'";
+            cmd.ExecuteNonQuery();
+            SqlDataReader reader = cmd.ExecuteReader();
+            if (reader.Read())
+            {
+                MessageBox.Show("该条码已存在！"); return;
+            }
+            reader.Close();
+            //没有则插入数据
             cmd.CommandText = $"insert into STM values('{barcode_tb.Text}','{STI_tb.Text}','{RTI_tb.Text}','{taskType_tb.Text}'," +
                                                     $"'{jobType_cbb.Text}','{startPoint_tb.Text}','{startLocation_tb.Text}','{endPoint_tb.Text}'," +
-                                                    $"'{endLocation_tb.Text}','{taskStatus_tb.Text}','{startTime_dtp.Text}','{errorInfor_tb.Text}')";
+                                                    $"'{endLocation_tb.Text}','{taskStatus_tb.Text}','{startTime_dtp.Value.ToString("yyyy-MM-dd HH:mm:ss")}','{errorInfor_tb.Text}')";
             Console.WriteLine(cmd.CommandText);
             int count = cmd.ExecuteNonQuery();
             if (count > 0)
@@ -83,5 +93,30 @@ namespace STS
         {
             Form2Closed?.Invoke(this, EventArgs.Empty);
         }
+
+        private void barcode_tb_Click(object sender, EventArgs e)
+        {
+            //如果是首次点击才执行以下代码
+            if (barcode_tb.Text.Equals("T*****"))
+            {
+                barcode_tb.Text = "";
+                barcode_tb.ForeColor = Color.Black;
+            }
+        }
+
+        private void barcode_tb_TextChanged(object sender, EventArgs e)
+        {
+
+        }
+
+        private void barcode_tb_MouseLeave(object sender, EventArgs e)
+        {
+
+        }
+
+        private void barcode_tb_HideSelectionChanged(object sender, EventArgs e)
+        {
+
+        }
     }
 }