组合框在if语句中无法识别字符串

我试图创建一个程序，该程序确定在组合框中选择什么字符串，然后将该字符串转换为要在计算中使用的整数。下面这段代码给我带来了麻烦。

我所有的组合框字符串返回错误:
类系统。字符串
将文本表示为一系列Unicode字符。

错误:
不能隐式地将类型'string'转换为'System.Windows.Forms.ComboBox'

            //Calculate Living Space replacement cost
            int livingSpaceSQ;
            int livingSpaceCostPerSF;
            int livingSpaceCost;
            if (cmbConstructionQuality = "Basic")
            {
                livingSpaceCostPerSF = 170;
            }
            if (cmbConstructionQuality = "Standard")
            {
                livingSpaceCostPerSF = 185;
            }
            if (cmbConstructionQuality = "Semi-Custom")
            {
                livingSpaceCostPerSF = 195;
            }
            else
            {
                livingSpaceCostPerSF = 225;
            }
            livingSpaceSQ = int.Parse(txtBuiltInGarage.Text.ToString());
            livingSpaceCost = livingSpaceSQ * livingSpaceCostPerSF;
            txtLivingSpaceCost.Text = livingSpaceCost.ToString();

我不太确定那是什么意思。我将如何使这个工作，以将选定的字符串转换为整数?

    if (cmbConstructionQuality.Text == "Basic")
    {
        livingSpaceCostPerSF = 170;
    }

        if (cmbConstructionQuality.Text == "Basic")
        {
            livingSpaceCostPerSF = 170;
        }
        else if (cmbConstructionQuality.Text =="Standard")
        {
            livingSpaceCostPerSF = 185;
        }
        else if (cmbConstructionQuality.Text == "Semi-Custom")
        {
            livingSpaceCostPerSF = 195;
        }
        else
        {
            livingSpaceCostPerSF = 225;
        }