试图跳过foreach语句C＃中的列

Question

我有一个我正在处理的库存管理程序。数据库和表系统的设置方式是每个类别都是不同的表。这是必要的，因为每个类别（即鞋子，电话，笔记本电脑）具有不同的字段以唯一地标识每个产品。因此，我创建了一个表，然后通过foreach语句添加名为columns的用户。我遇到的问题是它想要在已存在时添加ID列。我尝试嵌套在foreach中的添加一个If语句，但它只是打破了foreach循环。我只是没有找到一种方法让它跳过ID列并继续通过每个列来添加。

这是功能代码：

private void btnCreateCategory_Click(object sender, EventArgs e)
{
    List<string> FieldNames = new List<string>();

    foreach (var item in lstFieldNames.Items)
    {
        FieldNames.Add(lstFieldNames.Items.ToString());
    }

    DataTable NewCategory = new DataTable();
    NewCategory = CreateTable(FieldNames);
    dgPreviewAdd.DataSource = NewCategory;

    using (SqlConnection Connection = new SqlConnection(
       Helper.cnnVal("InventoryManager")))
    {
        using (SqlCommand command = new SqlCommand("", Connection))
        {
            command.CommandText = "Create Table tbl" + 
                NewCategory.TableName.ToString() + "(ID int)";

            Connection.Open();
            command.ExecuteNonQuery();
            Connection.Close();

            foreach (DataColumn newColumn in NewCategory.Columns)
            {
                 If( newColumn.ColumnName("ID")
                  {
                  }
                  Else
                  {
                SqlParameter colparam = new SqlParameter();
                colparam.ParameterName = "@ColumnName";
                colparam.Value = newColumn.ColumnName.ToString();

                SqlParameter tblParam = new SqlParameter();
                tblParam.ParameterName = "@TableName";
                tblParam.Value = "tbl" + NewCategory.TableName.ToString();

                command.Parameters.Add(colparam);
                command.Parameters.Add(tblParam);
                command.CommandText = "dbo.AddCategoryColumns";
                command.CommandType = CommandType.StoredProcedure;

                Connection.Open();
                command.ExecuteNonQuery();
                Connection.Close();
                }
            }

            LoadCategory catTableLoad = new LoadCategory();
            DataTable catTable = new DataTable();
            catTable = catTableLoad.getCategoryTable();

            SqlParameter param = new SqlParameter();
            param.ParameterName = "@CategoryName";
            param.Value = NewCategory.TableName.ToString();

            SqlParameter param2 = new SqlParameter();
            param2.ParameterName = "@IdNumber";
            param2.Value = catTable.Rows.Count + 1;

            command.Parameters.Add(param);
            command.Parameters.Add(param2);

            command.CommandText = "dbo.AddCategory";
            command.CommandType = CommandType.StoredProcedure;

            Connection.Open();
            command.ExecuteNonQuery();
            Connection.Close();
        }
    }
}

Answer 1

使用以下任何一种：

foreach (DataColumn newColumn in NewCategory.Columns)
{
    if (newColumn.ColumnName == "ID") continue;

    //Rest of logic goes here
}

或完全从循环中排除：

foreach (DataColumn newColumn in NewCategory.Columns.Where( c => c.ColumnName != "ID" ))
{

    //Rest of logic goes here
}

Answer 2

您可以使用distinct来对类别进行分组

不要忘记使用System.Linq添加;

private void btnCreateCategory_Click(object sender, EventArgs e)
    {
        List<string> FieldNames = new List<string>();

        foreach (var item in lstFieldNames.Items)
        {
            FieldNames.Add(lstFieldNames.Items.ToString());
        }

        var grpfieldNames = FieldNames.Distinct();

        DataTable NewCategory = new DataTable();

        NewCategory = CreateTable(grpfieldNames);

        dgPreviewAdd.DataSource = NewCategory;

        using (SqlConnection Connection = new SqlConnection(
           Helper.cnnVal("InventoryManager")))
        {
            using (SqlCommand command = new SqlCommand("", Connection))
            {
                command.CommandText = "Create Table tbl" +
                    NewCategory.TableName.ToString() + "(ID int)";

                Connection.Open();
                command.ExecuteNonQuery();
                Connection.Close();

                foreach (DataColumn newColumn in NewCategory.Columns)
                {
                    If(newColumn.ColumnName("ID")
                      {
                    }
                    Else
                      {
                        SqlParameter colparam = new SqlParameter();
                        colparam.ParameterName = "@ColumnName";
                        colparam.Value = newColumn.ColumnName.ToString();

                        SqlParameter tblParam = new SqlParameter();
                        tblParam.ParameterName = "@TableName";
                        tblParam.Value = "tbl" + NewCategory.TableName.ToString();

                        command.Parameters.Add(colparam);
                        command.Parameters.Add(tblParam);
                        command.CommandText = "dbo.AddCategoryColumns";
                        command.CommandType = CommandType.StoredProcedure;

                        Connection.Open();
                        command.ExecuteNonQuery();
                        Connection.Close();
                    }
                }

                LoadCategory catTableLoad = new LoadCategory();
                DataTable catTable = new DataTable();
                catTable = catTableLoad.getCategoryTable();

                SqlParameter param = new SqlParameter();
                param.ParameterName = "@CategoryName";
                param.Value = NewCategory.TableName.ToString();

                SqlParameter param2 = new SqlParameter();
                param2.ParameterName = "@IdNumber";
                param2.Value = catTable.Rows.Count + 1;

                command.Parameters.Add(param);
                command.Parameters.Add(param2);

                command.CommandText = "dbo.AddCategory";
                command.CommandType = CommandType.StoredProcedure;

                Connection.Open();
                command.ExecuteNonQuery();
                Connection.Close();
            }
        }
    }